CHAPTER XXXIV

GENERAL ARGUMENT AND CONCLUSION

THE problems concerned in the study of the floras of the Pacific islands from the standpoint of dispersal are here approached through the buoyant quality of the seed and fruit; and it is shown when dividing the plants into two groups, those with buoyant and those with non-buoyant seeds or fruits, that there has been at work through the ages a great sorting process, by which the plants belonging to the group first named have been mostly gathered at the coast. Its operation may be also observed within the limits of a genus, where the species possessing seeds or fruits that float is stationed at the coast, whilst the species with seeds or fruits that sink makes its home inland.

When the principle here involved is applied to the British flora, it presents itself as part of a much wider principle, by which plants endowed with buoyant seeds and fruits have been stationed at the water-side, whether on a river-bank, or beside a lake or pond, or on a sea-beach. The broader principle proves in its turn to belong to a far larger scheme, in which the fitness or unfitness of a plant to live in a physiologically dry station appears as the primary determining quality, the xerophyte (the plant of the dry station), provided with buoyant seed or fruit, finding its way to the coast, and the hygrophyte (the plant growing under more moist conditions), that is similarly endowed, establishing itself by the side of the river, or the lake, or the pond.

When dealing with the general character and composition of the strand-plants of the tropical Pacific, it is shown that in Fiji the beach-plants often assert their primary xerophilous habit or fitness for occupying any dry station by extending into the inland plains on the dry sides of the islands. The Fijian shore-plants are divided into three formations, those of the beach, those of the mangrove-swamp, and those of intermediate stations on the borders of the swamps. The great majority of the Fijian shore-plants are dispersed by the currents. The Tahitian Islands, which are representative of Eastern Polynesia, lack the mangroves and most of the plants that grow at the margin of a mangrove-swamp; and their strand-flora is mainly composed of plants of the beach, such as are dispersed by the currents far and wide in tropical regions. The Hawaiian strand-flora is very meagre in its character, lacking not only the plants of the mangrove and intermediate formations, but almost all the large-fruited beach-trees of the South Pacific. Since Hawaii possesses but few current-dispersed shore-plants that are not found in the New World, reasons are given for the inference that such shore-plants were originally brought by the currents from America, and not from the South Pacific.

We are led on various grounds to the conclusion that tropical shore-plants distributed by currents belong to two great regions, the American including the west coast of Africa, and the Asiatic, or Old World Region, which includes the African east coast. It is held that America is so placed with regard to the currents, that it is a distributor, and not a recipient of tropical shore-plants dispersed by that agency. From this it follows that all cosmopolitan tropical beach-plants that are dispersed by the currents have their homes in America.

The results of observation and experiment are given to show that there is no direct relation between the specific weight of seeds and fruits and the density of sea-water. Yet, although the floating or sinking of a seed or fruit is but an accidental attribute, it has had indirectly a far-reaching influence not only on plant-distribution, but on plant-development. In accordance with this want of relation between the specific weight of seeds and fruits and the density of sea-water, the great variety of structures concerned with buoyancy are regarded in the main, after a detailed examination of their character, as not arising from adaptation. Rather, it is urged, is buoyancy connected with structures that now serve a purpose for which they were not originally developed. Nature, it is held, has never concerned herself directly with providing means of dispersal of any sort.

In the discussion of the relation between the littoral and inland Pacific floras, it is shown, as a result of the examination of those genera possessing both shore and inland species, that they have been on the whole developed on independent lines. Two special difficulties in explaining the modes of dispersal of plants of the Pacific islands here come into prominence. There is the Hawaiian difficulty, where with genera containing both shore and inland species only the last are found in Hawaii; and although the shore-plants are known to be dispersed by the current, the inland plants display little or no capacity for this or any other mode of dispersal. Here belong the Leguminous genera Canavalia, Erythrina, Mezoneuron, and Sophora, and the Apocynaceous genus Ochrosia; and it is assumed that the inland Hawaiian species are derived from a current-dispersed shore-plant that has since disappeared from the group. The Fijian difficulty is displayed in those genera where both coast and inland species occur in the islands, but no known existing means of dispersal across an ocean can be postulated for the inland plants, though the shore species are distributed by the currents. Of such genera Pandanus is the best example, and it is pointed out that this genus presents the same difficulty in the Mascarene Islands, in which case the agency of the extinct Columbæ is invoked.

As illustrating the methods of observation and experiment employed by the author, the Leguminous shore-plants Afzelia bijuga, Cæsalpinia bonducella, and Entada scandens are discussed at length; and in the chapters on the enigmas of the Leguminosæ in the Pacific it is pointed out that the behaviour of the plants of this order is a source of much perplexity, and that they conform to no single rule of dispersal.

Coming to the inland plants of this region, the Fijian, Tahitian, and Hawaiian groups are taken as the chief centres of distribution in the Pacific. After discussing the relative sizes, the altitudes, and the climates of these three archipelagoes, it is shown that Hawaii, on account of the far greater altitude of the islands, is characterised by a special mountain flora, and that it is comparable with Fiji, and to a great extent also with Tahiti, only as regarding the plants of the levels below 4,000 or 5,000 feet.

The first era of the plant-stocking is designated the Age of Ferns, and it is observed that, whilst in Hawaii nearly half of the ferns and lycopods are peculiar to that group, very few new species have been developed in the Fijian and Tahitian regions.

The next era in the floral history of these islands is represented in the first era of the flowering plants. This is indicated by the endemic genera, which are particularly numerous in Hawaii, relatively scanty in Fiji, and very few in Tahiti. On account of their preponderance, the era is designated the Age of Compositæ and Lobeliaceæ. The genera of these two orders, though mainly characteristic of Hawaii, are also to be found in the Tahitian region, but they are absent from the Fijian area. Chiefly American in their affinities, their dispersion over the Pacific took place during the Tertiary submergence of the archipelagoes of the Western Pacific, in which are included the groups of the Fijian area (Fiji, Samoa, Tonga). These early forms of Compositæ and Lobeliaceæ are often arborescent in habit; and it is observed that Tree-Lobelias also occur high up the slopes of lofty mountains in tropical regions, as in Equatorial Africa, under conditions similar to those prevailing on the slopes of the Hawaiian mountains, where the Tree-Lobelias, termed by Dr. Hillebrand “the pride of our flora,” abound.

The other Hawaiian endemic genera, marking the first chapter in the history of the flowering plants, arrange themselves in two groups, one chiefly American in general affinities, and containing highly differentiated Caryophyllaceæ, Labiatæ, &c.; the other largely Malayan, and indicating the close of the first era of the flowering plants, when the main source of the plants was shifted from America to the Old World. The Fijian endemic genera, which are few in number, miscellaneous in appearance, and disconnected in character, are regarded as having probably acquired their endemic reputation through their failure at their sources in the regions to the west.

The second era of the flowering plants is indicated by the non-endemic genera. Here we are concerned on the one hand with a mountainous flora mainly Hawaiian, in which genera from the New Zealand and Antarctic floras take a conspicuous part, and on the other with a low-level flora chiefly derived from Indo-Malaya, and including the plants of the lower slopes of Hawaii below 4,000 and 5,000 feet, and the floras in mass of Fiji and Tahiti.

On account of their lower altitude, the extensive mountain flora of Hawaii is but scantily developed in Tahiti, and is represented by a mere remnant in Fiji and Samoa. Two-thirds of the Hawaiian non-endemic mountain genera contain only species restricted to the group, and, although amongst these disconnected genera, Acæna, Gunnera, Coprosma, Lagenophora, &c., of the New Zealand and Antarctic floras take a prominent part, a large proportion of the genera like Ranunculus, Rubus, Artemisia, Vaccinium, and Plantago represent generally the flora of the north temperate zone on the summits of tropical mountains. The Tahitian mountain flora, scanty as it is when judged by the non-endemic genera, displays much kinship with the Hawaiian mountain flora; but this kinship is mainly confined to genera from high southern latitudes, such as Coprosma, Cyathodes, Astelia, &c. In the possession on its mountain slopes of the three genera of the Coniferæ, Dammara, Podocarpus, and Dacrydium, the Fijian region is distinguished from that of Tahiti and Hawaii; and it is assumed that they mark the site of a continental area in the Mesozoic period, when the Tahitian and Hawaiian groups did not exist.

The era of the non-endemic genera, in so far as it is concerned with the low-level flora of Hawaii and the floras in mass of the areas of Fiji, Samoa and East Polynesia, is termed Malayan, because many of the genera are thence derived. Here we are dealing with all the oceanic groups of the tropical Pacific, and not with a portion of them, as in the case of the Age of Coniferæ, in the Secondary period, that was limited to the Western Pacific, or in the case of the Age of Compositæ and Lobeliaceæ that was restricted during the Tertiary epoch to the Hawaiian and Tahitian regions. The first part of this era, as is indicated by the endemic species, is an age of complete isolation in Hawaii, and of partial isolation in the groups of the southern region. Amongst the genera typical of this period are Pittosporum, Gardenia, Psychotria, Cyrtandra, and Freycinetia. A later period in this era of the general dispersal of Malayan plants over the Pacific is one where the extremely variable or polymorphous species plays a conspicuous part, as represented in such genera as Alphitonia, Dodonæa, Metrosideros, Pisonia, and Wikstrœmia, the general principle being that each genus is at first represented by a widely ranging very variable species, which ultimately ceases to wander and settles down, and becomes the parent of different sets of species in the several groups.

The facts of distribution in this age of general dispersion are just such as we might look for in the case of a general dispersal over the oceanic groups of the Pacific, with the altitudes of the islands playing a determining part. But it should be remarked that the greater number of the genera that have entered the Pacific from the Old World have not advanced eastward of the Fijian region, half of the Fijian genera not occurring in the Hawaiian and Tahitian regions. The explanation of this is to be found, not in any lack of capacities for dispersal, but in a want of opportunities. The story of plant-distribution in the Pacific is bound up with the successive stages of decreasing activity in the dispersing agencies. The area of active dispersion, as illustrated by the non-endemic genera, at first comprised the whole of the tropical Pacific. It was afterwards restricted to the South Pacific, and finally to the Western Pacific only. The birds that carried seeds all over this ocean became more and more restricted in their ranges, probably on account of increasing diversity of climatic conditions. The plants of necessity responded to the ever narrowing conditions of bird-life in this ocean, and the differentiation of the plant and the bird have taken place together.

During the stages of decreasing activity in the dispersing agencies, the widely-ranging highly variable species continued to be an important factor in the development of new species in the different groups. The _rôle_ of the polymorphous species has always been a conspicuous one in the Pacific.

Yet, as in the case of the Cyrtandras, it is shown that the display of great formative power within a genus is not a peculiarity of an insular flora; that the isolation of an oceanic archipelago does not exclusively induce “endemism,” but only intensifies it; that the development of new species may be nearly as active on a mountain in a continent as on an island in mid-ocean; and that this is equally true of a land genus, like Embelia, exposed to an infinite variety of conditions, and of an aquatic genus, like Naias, where the conditions of existence are relatively uniform all the world over.

In framing a scheme by which the eras of the floral history of the Pacific are brought into correlation with those of geological time, the age of the Coniferæ is placed in the Secondary period, that of the Compositæ and Lobeliaceæ in the Tertiary period, whilst the era of Malayan immigration is regarded as mainly post-glacial. The age of the Coniferæ is concerned only with the Western Pacific, since the Hawaiian and Tahitian islands had not then been formed. The age of the Compositæ and Lobeliaceæ is concerned only with Hawaii and Tahiti, since the islands of the Western Pacific were then more or less submerged. That of the Malayan plants affects the whole Pacific as at present displayed to us.

In the chapter on the viviparous mangroves of Fiji it is shown that both the Asiatic and the American species of Rhizophora (R. mucronata and R. mangle) exist in that group, and that there is in addition a seedless form, the Selala, which, although intermediate in character between the two other species, comes nearest to the Asiatic plant. Reasons are given for the belief that the Selala is derived from the Asiatic species (R. mucronata), not as the result of a cross but as connected with its dimorphism; and in support of this it is pointed out that on the Ecuador coast of South America, where only the American species exists, a dimorphism is also displayed, one of the forms approaching in several of its characters the Fijian Selala, though fruiting abundantly and bearing the impress of a closer connection with the typical American species than with the Asiatic plant. The view that Rhizophora mangle reached the Western Pacific from America is rejected, and it is considered that this species was originally as widely diffused in the Old World as in America, and that it now survives only in a few places in the tropics of the Old World. The results of detailed observations on the modes of dispersal and on the germinating process both with Rhizophora and Bruguiera are given; and the absence, as a general rule, of any period of rest between the fecundation of the ovule and the germination of the seed is established.

A special chapter is devoted to the significance of vivipary, and it is considered that a record of the history of vivipary on the globe is afforded in the scale of germinative capacity that begins with the seedling hanging from a mangrove and ends with the seed that is detached in an immature condition from an inland plant. It is suggested that with the drying up of the planet in the course of ages the viviparous habit, which was once nearly universal, has been for the most part lost except in the mangrove swamp, which to some extent represents an age when the earth was enveloped in cloud and mist and the atmosphere was saturated with aqueous vapour. The lost habit is at times revived in the abnormal vivipary of some inland plants, and traces of it are seen in the abnormal structure of the seeds of some genera of the Myrtaceæ, like Barringtonia, and in the seeds of genera of other orders. With the desiccation of the planet and the emergence of the continents there has been continual differentiation of climate resulting in seasonal variation and in the development of the rest-period of the seed.

With the secular drying of the globe and the consequent differentiation of climate is to be connected the suspension to a great extent of the agency of birds as plant-dispersers in later ages, not only in the Pacific Islands but over all the tropics. The changes of climate, bird, and plant have gone on together, the range of the bird being controlled by the climate, and the distribution of the plant being largely dependent on the bird.

The history of climate, the history of the continents and of the oceans, the history of life itself, but only in the sense below defined, all belong to that of a desiccating world, or rather of a planet once sunless and enveloped in mist and cloud, that through the ages has been drying up. Life’s types were few and the sea prevailed, and one climate reigned over the globe. With the diminution of the aqueous envelopes the continents began to emerge, climates began to individualise, and organisms commenced to differentiate, and thus the process has run on through the past, ever from the general to the special both in the organic and in the inorganic world.

The same story of a world drying up is told by the marine remains left stranded far up some mountain slope, or by the bird akin to no other of its kind that Time has stranded on some island in mid-Pacific. The bird generalised in type that once ranged the globe is now represented over its original range by a hundred different groups of descendants, confined each to its own locality. Climate, once so uniform, now so diversified, has by restricting the range of the bird favoured the process of differentiation, and the plant dependent on the bird for its distribution has in its turn responded to these changes.

The _rôle_ of the polymorphous species belongs alike to the plant and to the bird. A species that covers the range of a genus varies at first in every region and ultimately gives birth to new species in some parts of its range. Then the wide-ranging species disappears and the original area is divided up into a number of smaller areas each with its own group of species. Each smaller area breaks up again, and forms, yet more specialised, are produced; and thus the process of subdivision of range and of differentiation of form goes along until each island in an archipelago owns its bird and each hill and valley has its separate plants. This is not the path that Evolution takes, since beyond lies extinction whether of plant or of bird. Such is the upshot of the process of differentiation exhibited in the development of species and genera in the Pacific Islands, or, indeed, in any oceanic groups. It can never do more than produce a Dodo or a Kiwi, or amongst the plants a Tree-Lobelia.

Evolution here and elsewhere is a thing apart from species and genera, which are but eddies on the surface of its stream. It is a scheme of life introduced into a much conditioned world, and adaptation in endless forms is the price it has had to pay. The whole story of life on this earth is a story of a sacrifice, of an end to be won, but of a price to be paid. Immortality is in the scheme, but death is the price of adaptation. The same theme runs through our conceptions of the spiritual life. There is the same duality, evolution adapting its scheme to the exigencies of the physical world, the good principle ever in conflict with the evil, and at times compelled to adapt itself to attain its ends. There is the tale of adaptation in the one case and of sacrifice in the other, and success is reached in both.

APPENDIX

LIST OF NOTES

Note 1. On the number of known species of Fijian flowering plants.

Note 2. The littoral plants of Fiji.

Note 3. Results of long flotation experiments on the seeds or seedvessels of tropical littoral plants.

Note 4. Table illustrating the degree of buoyancy of the seeds and fruits of inland Fijian plants.

Note 5. The inland Fijian plants possessing buoyant seeds or fruits.

Note 6. Table showing the degree of buoyancy of the seeds and fruits of some inland Hawaiian plants.

Note 7. Some inland Hawaiian plants possessing buoyant seeds or fruits.

Note 8. The pyrenes of Morinda.

Note 9. The buoyancy of the fruits of Calophyllum.

Note 10. The buoyancy experiments on British plants.

Note 11. The effect of sea-water immersion on the germinating capacity of seeds and seed-vessels.

Note 12. The buoyancy of the fruits of Galium aparine.

Note 13. The buoyancy of the seeds of Convolvulus sepium.

Note 14. Other long flotation experiments.

Note 15. The occurrence inland of Silene maritima.

Note 16. The buoyancy of the seeds or fruits of the British beach-plants that also occur inland.

Note 17. The buoyancy of the seeds or fruits of the British littoral plants that frequent salt-marshes and muddy shores.

Note 18. The buoyancy of the seeds or fruits of the British littoral plants that are confined to the beach.

Note 19. On germination in sea-water.

Note 20. On the maximum heights reached by some shore plants in their extension inland in Vanua Levu, Fiji.

Note 21. On the dwarfing of shore plants when extending inland in the “talasinga” plains in Vanua Levu.

Note 22. The “talasinga” plains of Vanua Levu.

Note 23. Schimper’s grouping of the Indo-Malayan strand flora.

Note 24. Grouping of some of the characteristic plants of the strand flora of Fiji.

Note 25. The strand flora of the Tahitian region.

Note 26. The Fijian shore plants not found in Tahiti.

Note 27. The intruders into the beach flora from the inland plants of Tahiti.

Note 28. The littoral plants of the Hawaiian islands.

Note 29. Botanical notes on the coast plants of the Hawaiian islands.

Note 30. The beach drift of the Hawaiian islands.

Note 31. The inland extension of the shore plants of the Hawaiian islands.

Note 32. The Fijian species of Premna.

Note 33. De Candolle’s list of plants dispersed exclusively by currents.

Note 34. The littoral plants of the eastern-most Polynesian islands.

Note 35. Distribution of the littoral plants with buoyant seeds or fruits that occur in the Fijian, Tongan, Samoan, Tahitian, and Hawaiian Groups.

Note 36. Hawaiian plants with buoyant seeds or fruits known to be dispersed by the currents either exclusively or with the assistance of frugivorous birds.

Note 37. On vivipary in the fruits of Barringtonia racemosa and Carapa obovata.

Note 38. On the temperature and density of the surface water of the estuaries of the Rewa River in Fiji and of the Guayaquil River in Ecuador.

Note 39. On the Pacific species of Strongylodon.

Note 40. Precautions in testing seed-buoyancy.

Note 41. The buoyancy of the seeds of Convolvulus soldanella in fresh-water and sea-water compared.

Note 42. On secular changes in sea-density.

Note 43. On the mucosity of small seeds and seed-like fruits when wet.

Note 44. Upon the effects of inland extension on the buoyancy of the seeds or fruits of littoral plants.

Note 45. Tabulated results of the classification, according to Schimper’s application of the Natural Selection Theory, of the buoyant seeds and fruits of tropical littoral plants.

Note 46. On the modes of dispersal of the genus Brackenridgea.

Note 47. On the transport of gourds by currents.

Note 48. On the useless dispersal by currents of the fruits of the Oak and of other species of Quercus, as well as of the Hazel (Corylus).

Note 49. On the distribution of Ipomœa pes capræ, Convolvulus soldanella, and Convolvulus sepium.

Note 50. On the structure of the seeds and fruits of Barringtonia.

Note 51. On a common inland species of Scævola in Vanua Levu, Fiji.

Note 52. On the capacity for dispersal by currents of Colubrina oppositifolia.

Note 53. On the genus Erythrina.

Note 54. On the genus Canavalia.

Note 55. The inland extension of Scævola kœnigii.

Note 56. On the capacity for dispersal by currents of Sophora tomentosa, S. chrysophylla, and S. tetraptera.

Note 57. On the species of Ochrosia.

Note 58. On Pandanus.

Note 59. Seeds in petrels.

Note 60. Schimper on the halophilous character of littoral Leguminosæ and of shore plants generally.

Note 61. Meteorological observations on the summit of Mauna Loa.

Note 62. On the relative proportion of vascular cryptogams in Fiji.

Note 63. On the table of vascular cryptogams of Tahiti, Hawaii, and Fiji.

Note 64. On the distribution of the Tahitian ferns and lycopods.

Note 65. Distribution of some of the mountain ferns of Hawaii that are not found either in Fiji or in Tahiti.

Note 66. Endemic genera of ferns in Hawaii.

Note 67. On the dispersal of Compositæ by birds.

Note 68. On some of the Hawaiian endemic genera excluding those of the Compositæ and Lobeliaceæ.

Note 69. On the germination of Cuscuta.

Note 70. On beach-temperature.

Note 71. On the buoyancy of the seeds or seed-vessels of some Chilian shore plants.

Note 72. On the southern limit of the mangrove formation in Ecuador.

Note 73. Additional note on the temperature of the dry coast of Ecuador, between the island of Puna and the equator.

Note 74. Observations on the temperature of the Humboldt current from Antofagasta northward between January and March, 1904.

Note 75. On the stranded massive corals of the genus Porites (?) found on the coast of North Chile and Peru at Arica, Callao, and Ancon.

Note 76. Stranded pumice on English and Scandinavian beaches.

Note 77. On the mode of dispersal of Kleinhovia hospita.

Note 78. On the “Sea”, an unidentified wild fruit tree in Fiji.

Note 79. On willow-leaved river-side plants.

Note 80. Mr. Perkins on the Hawaiian Lobeliaceæ.

Note 81. On the vertical range of some of the most typical and most conspicuous of the plants in the forests on the Hamakua slopes of Mauna Kea, Hawaii.

Note 82. Aboriginal weeds.

Note 90. On the buoyancy of the seeds of Euphorbia amygdaloides and E. segetalis.

Note 91. Mr. E. Kay Robinson on Aster tripolium.

NOTE 1 (page 13)

ON THE NUMBER OF KNOWN SPECIES OF FIJIAN FLOWERING PLANTS

Rather over 600 species of flowering plants are included in Seemann’s _Flora Vitiensis_, excluding the weeds and the plants introduced by man. Horne’s collections would probably add another 300 species; and many more remain to be discovered.

NOTE 2 (page 13)

THE LITTORAL PLANTS OF FIJI

In the following table are incorporated the results of an extensive series of observations and experiments on the buoyancy of the seeds and fruits of the shore plants made by the author during his sojourn of two years in Fiji, and based not only on prolonged buoyancy-tests, but also on systematic examination of the stranded and floating seed-drift, both of sea and river. The details would occupy many chapters: and it is only possible here to give the bare results. Since Professor Schimper went over much the same ground in the Malayan region, one enjoys in many cases the great advantage of his authority; but a fair proportion of the results are new; and, besides, there are a number of plants included, the buoyancy of whose seeds or fruits has long been well established. In all cases the seed or fruit is taken as it presents itself for dispersal by the currents. Many of the plants are discussed with some detail in various parts of this book, as indicated in the reference column of the table.

Since the Gramineæ and the Cyperaceæ contain very few species suited for direct transport by the currents over wide areas of sea, this list may be regarded as containing nearly all the littoral flowering plants possessing seeds or seed-vessels with any buoyancy of importance.

Nearly all the Tahitian strictly littoral plants are represented in Fiji, and the few that have not been found there yet, such as Sesbania grandiflora, Heliotropium anomalum, &c., may exist, as in the first-named species, in the neighbouring Tongan group, and may probably even exist in Fiji. Two other Tahitian littoral plants, that are widely spread in the Pacific, namely, Suriana maritima and Sesuvium Portulacastrum, are found in Tonga, and are included in my list of Fijian shore plants, though not yet recorded from that group, where, however, they will, without a doubt, be found by some future observer.

TABLE SHOWING THE BUOYANCY OF THE SEEDS OR FRUITS OF THE LITTORAL PLANTS OF FIJI, EXCLUDING THE GRASSES AND, WITH ONE EXCEPTION, THE SEDGES

The letters placed before the plant name indicate that the species is also found in Hawaii (H), in Tahiti (T), and in the Marquesas (M). The Marquesan locality is only given where the plant is not in Tahiti.

The abbreviations in the reference column are as follows:

S=Schimper; G=Guppy; P=Earlier authorities and particularly the list given by Hemsley in the Introduction to the _Botany of the Challenger Expedition_.

Column headings:

A. Buoyancy of seeds or fruits. B. Float for months. C. Sink at once or in a week or two. D. Authorities. E. Pages of further reference. See also Index.

+--------------------------------------+--------------+-------+-------+--------+ | | | A | | | | Species. | Family. +---+---+ D | E | | | | B | C | | | +--------------------------------------+--------------+---+---+-------+--------+ |HT Calophyllum inophyllum |Guttiferæ. | + |...|S.G.P. | 18 | | | | | | | | |HT Hibiscus tiliaceus |Malvaceæ. | + |...|S.G.P. | 21 | | | | | | | | | Hibiscus diversifolius (Jacq.) |Malvaceæ. | + |...|G. | 21 | | | | | | | | |HT Thespesia populnea |Malvaceæ. | + |...|S.G.P. | Note 3 | | | | | | | | | H Gossypium tomentosum (Nutt.) |Malvaceæ. |...| + |G. | | | | | | | | | | Heritiera littoralis |Sterculiaceæ. | + |...|S.G.P. | 45, 48 | | | | | | | | | T Kleinhovia hospita |Sterculiaceæ. | + |...|G. | 21 | | | | | | | | | T Triumfetta rhomboidea |Tiliaceæ. |...| +?| | | | | | | | | | | T Triumfetta procumbens |Tiliaceæ. |...| + |G. | 45 | | | | | | | | | T Suriana maritima |Simarubeæ. | + |...|S.G. | | | | | | | | | | Carapa moluccensis |Meliaceæ. | + |...|S.G.P. | 45 | | | | | | | | | Carapa obovata |Meliaceæ. | + |...|S.G.P. | 45 | | | | | | | | | T Ximenia americana |Olacineæ. | + |...|S.G. | 113 | | | | | | | | | Smythea pacifica (Seem.) |Rhamneæ. | + |...|G.P. | 106 | | | | | | | | |HT Colubrina asiatica |Rhamneæ. | + |...|G. | 137 | | | | | | | | |HT Dodonæa viscosa |Sapindaceæ. | + |...|S.G. | | | | | | | | | |HT Tephrosia piscatoria |Papilionaceæ. |...| + |G. | 45 | | | | | | | | | M Desmodium umbellatum |Papilionaceæ. |...| + |G. | | | | | | | | | |HT Dioclea violacea |Papilionaceæ. | + |...|G.P. | 82 | | | | | | | | | T Canavalia obtusifolia |Papilionaceæ. | + |...|S.G.P. |Note 54 | | | | | | | | | T Canavalia sericea |Papilionaceæ. | + |...|G. |Note 54 | | | | | | | | | T Canavalia ensiformis, var. turgida.|Papilionaceæ. | + |...|S.G.P.?|Note 54 | | | | | | | | |HT Mucuna gigantea |Papilionaceæ. | + |...|S.G.P. | 81 | | | | | | | | | T Erythrina indica |Papilionaceæ. | + |...|S.G.P. | | | | | | | | | |HT Strongylodon lucidum |Papilionaceæ. | + |...|G. | 82 | | | | | | | | |HT Vigna lutea |Papilionaceæ. | + |...|S.G. | 139 | | | | | | | | | Dalbergia monosperma |Papilionaceæ. | + |...|S.G. | 106 | | | | | | | | | Derris uliginosa |Papilionaceæ. | + |...|S.G.P. | 111 | | | | | | | | | Pongamia glabra |Papilionaceæ. | + |...|S.G.P. | | | | | | | | | | T Sophora tomentosa |Papilionaceæ. | + |...|S.G. |Note 56 | | | | | | | | | T Inocarpus edulis |Papilionaceæ. | +?|...|G.P. | | | | | | | | | |HT Cæsalpinia Bonducella |Cæsalpinieæ. | + |...|S.G.P. | 193 | | | | | | | | | T Cæsalpinia Bonduc |Cæsalpinieæ. | + |...|G.P. | 193 | | | | | | | | | Afzelia bijuga |Cæsalpinieæ. | + |...|G. | 173 | | | | | | | | | Cynometra sp. |Cæsalpinieæ. | +?|...|S.G. | | | | | | | | | | Entada scandens |Mimoseæ. | + |...|G.P. | 181 | | | | | | | | | Acacia laurifolia |Mimoseæ. |...| + |G. | 164 | | | | | | | | | T Leucæna Forsteri |Mimoseæ. |...| + |G. | | | | | | | | | | T Serianthes myriadenia |Mimoseæ. |...| + |G. | 424 | | | | | | | | | Parinarium laurinum |Rosaceæ. | + |...|G.P. | | | | | | | | | | Eugenia Richii |Myrtaceæ. |...| + |G. | | | | | | | | | | T Barringtonia speciosa |Myrtaceæ. | + |...|S.G.P. | | | | | | | | | | Barringtonia racemosa |Myrtaceæ. | + |...|G. | | | | | | | | | | Rhizophora mucronata |Rhizophoreæ. | + |...|S.G.P. | | | | | | | | | | Rhizophora mangle |Rhizophoreæ. | + |...|S.G.P. | | | | | | | | | | Bruguiera Rheedii |Rhizophoreæ. | + |...|G.P. | | | | | | | | | |HT Terminalia Katappa |Combretaceæ. | + |...|S.G.P. | | | | | | | | | | M Terminalia littoralis |Combretaceæ. | + |...|S.G.P. | | | | | | | | | | Lumnitzera coccinea |Combretaceæ. | + |...|S.G.P. | | | | | | | | | | T Gyrocarpus Jacquini |Combretaceæ. | + |...|G. | 423 | | | | | | | | | T Pemphis acidula |Lythraceæ. | + |...|S.G. | | | | | | | | | | T Luffa insularum (Gray) |Cucurbitaceæ. | + |...|G. | 426 | | | | | | | | |HT Sesuvium Portulacastrum |Ficoideæ. |...| + |G. | | | | | | | | | |HT Morinda citrifolia |Rubiaceæ. | + |...|S.G.P. | | | | | | | | | | T Guettarda speciosa |Rubiaceæ. | + |...|S.G.P. | | | | | | | | | | T Wedelia biflora |Compositæ. | + |...|G. | | | | | | | | | |HT Scævola Koenigii |Goodeniaceæ. | + |...|S.G.P. | | +--------------------------------------+--------------+---+---+-------+--------+

TABLE SHOWING THE BUOYANCY OF THE SEEDS OR FRUITS OF THE LITTORAL PLANTS OF FIJI, EXCLUDING THE GRASSES, AND WITH ONE EXCEPTION, THE SEDGES (_continued_)

Column headings:

A. Buoyancy of seeds or fruits. B. Float for months. C. Sink at once or in a week or two. D. Authorities. E. Pages of further reference. See also Index.

+--------------------------------------+--------------+-------+-------+--------+ | | | A | | | | Species. | Family +---+---+ D | E | | | | B | C | | | +--------------------------------------+--------------+---+---+-------+--------+ | T Cerbera Odollam |Apocynaceæ. | + |...|S.G.P. | | | | | | | | | | T Ochrosia parviflora |Apocynaceæ. | + |...|G.P. | | | | | | | | | |HT Cordia subcordata |Boraginaceæ. | + |...|S.G.P. | | | | | | | | | | T Tournefortia argentea |Boraginaceæ. | + |...|S.G.P. | | | | | | | | | |HT Ipomœa pes capræ |Convolvulaceæ.| + |...|S.G.P. | | | | | | | | | | H Ipomœa glaberrima (Boj.) |Convolvulaceæ.| + |...|G. | | | | | | | | | | Aniseia uniflora |Convolvulaceæ.| + |...|G. | | | | | | | | | | T Premna tahitensis |Verbenaceæ. | + |...|G. |Note 32 | | | | | | | | | Clerodendron inerme |Verbenaceæ. | + |...|S.G. | | | | | | | | | |HM Vitex trifolia |Verbenaceæ. | + |...|G. | | | | | | | | | |HT Cassytha filiformis |Lauraceæ. | + |...|G. | | | | | | | | | | T Hernandia peltata |Lauraceæ. | + |...|S.G. | | | | | | | | | |HT Wikstrœmia fœtida |Thymelæaceæ. |...| + |G. | | | | | | | | | | Drymispermum Burnettianum |Thymelæaceæ. |...| + |G. | | | | | | | | | | T Euphorbia Atoto |Euphorbiaceæ. |...| + |S.P.G. | | | | | | | | | | Excæcaria Agallocha |Euphorbiaceæ. | + |...|S.G. | | | | | | | | | | T Casuarina equisetifolia |Casuarineæ. |...| + |G. | | | | | | | | | |HT Tacca pinnatifida |Taccaceæ. | + |...|G. | 19 | | | | | | | | |HT Cocos nucifera |Palmeæ. | + |...|P. | | | | | | | | | |HT Pandanus odoratissimus |Pandaneæ. | + |...|S.G.P. | | | | | | | | | | Crinum asiaticum |Amaryllideæ. |...| + |G.P. | | | | | | | | | | Scirpodendron costatum |Cyperaceæ. | + |...|G. | 407 | | | | | | | | | Cycas circinalis |Cycadeæ. | + |...|G.P. | | +--------------------------------------+--------------+---+---+-------+--------+

NOTE 3 (page 13)

RESULTS OF LONG FLOTATION EXPERIMENTS ON THE SEEDS OR SEED-VESSELS OF TROPICAL LITTORAL PLANTS

At various times during the past twenty years I have made lengthened experiments in England on the buoyancy in sea-water of the seeds or seed-vessels of beach plants collected by me in the Solomon Islands, the Fijis, Hawaii, Keeling Atoll, &c. In all the species enumerated below, the floating powers were retained after twelve months’ immersion, the seed-contents being to all appearance unharmed. In six species I succeeded in getting the seeds to germinate after the experiment; and there can be no doubt that the number of successful results would have been largely increased, if I had not been obliged to resort to very primitive methods in conducting the experiments. Some of the results are referred to in a note to my paper on the flora of Keeling Atoll, dated about 1889; and if I remember aright, Mr. Hemsley mentioned those relating to Thespesia populnea and Ipomœa grandiflora in the _Annals of Botany_, not long after. The others have not been previously published. In one instance (Cæsalpinia bonducella) the flotation experiment was prolonged to two and a half years, the seeds floating buoyantly and being apparently quite sound at the end of the experiment.

As demonstrating that tropical seeds can be transported unharmed by currents through cold latitudes, it should be noted that all these experiments were conducted in England. In the cases of the Keeling Atoll seeds the experiment was carried on through a very severe winter, the vessel of sea-water being exposed to a degree of cold that kept fresh-water frozen for three weeks on the same table. This did not prevent the subsequent germination of the seeds of Thespesia populnea and Ipomœa grandiflora. The same thing was established in a more natural way by Lindman, who planted seeds of Entada scandens and Mucuna urens, that had been stranded on the Norwegian coast, and found that they retained their germinating capacity (see Sernander, p. 7).

The following are the seeds or seed-vessels that remained afloat after a year’s flotation in sea-water, those that subsequently germinated being preceded by G. In the other cases the germinating capacity was not tested; but they were always sound in appearance when cut across at the close of the experiment.

G Thespesia populnea (Malvaceæ) Dioclea (violacea?) (Papilionaceæ) G Mucuna gigantea, D C (Papilionaceæ) G Mucuna urens, D C (Papilionaceæ) Mucuna, sp. (Papilionaceæ) Mucuna, sp. (Papilionaceæ) G Strongylodon lucidum, Seem. (Papilionaceæ) Sophora tomentosa, (Papilionaceæ) G Cæsalpinia bonducella (Cæsalpinieæ) Entada scandens (Mimoseæ) Morinda citrifolia (Rubiaceæ) Scævola Koenigii (Goodeniaceæ) Cordia subcordata (Boragineæ) Tournefortia argentea (Boragineæ) G Ipomœa grandiflora, Lam. (Convolvulaceæ) Tacca pinnatifida (Taccaceæ)

NOTE 4 (page 13)

TABLE ILLUSTRATING THE DEGREE OF BUOYANCY OF THE SEEDS AND FRUITS OF INLAND FIJIAN PLANTS

(Unless otherwise indicated, the seeds or fruits sink at once or in a day or two)

Abrus precatorius. Acacia Richii. Ageratum conyzoides. Alphitonia excelsa. Alpinia sp. Alyxia (scandens?). Artocarpus incisa. Artocarpus integrifolia. Barringtonia edulis (1 month) Barringtonia sp. Bauhinia sp. Bischoffia javanica. Cæsalpinia sp. Calophyllum spectabile (2-4 weeks). Calophyllum Burmanni (4-10 days). Cananga odorata. Canarium sp. Canarium sp. Canna indica. Citrus aurantium (3-4 weeks). Citrus decumana (1 month). Citrus limonum (5 weeks). Citrus vulgaris, R. (6-7 weeks). Coix lachryma (2-7 days). Commersonia platyphylla. Cordyline sepiaria. Couthovia corynocarpa (a few days). Cucumis acidus (a few days). Cucurbita sp. (several months). Cupania sp. Dammara vitiensis (7-10 days). Dioscorea sativa (a few days). Dioscorea sp. Dracontomelon sylvestre. Dracontomelon sp. Elæocarpus sp. Elæocarpus sp. (a few days). Eranthemum sp. Eugenia malaccensis (2-4 weeks). Eugenia effusa? (4-7 days). Eugenia confertiflora? (10-12 days). Eugenia rariflora (a few days). Eugenia corynocarpa (a few days). Eugenia rivularis (a week). Fagræa Berteriana (a few days). Ficus Harveyi (7-10 days). Ficus scabra (7-10 days). Ficus sp. (7-10 days). Gardenia vitiensis (4-5 weeks). Geissois ternata. Geophila reniformis. Gnetum gnemon. Grewia sp. Guettarda sp. (a few weeks). Hibiscus Abelmoschus (months). Hibiscus seculentus. Hydrocotyle asiatica (months). Ipomœa batatas. Ipomœa insularis (_nil_ or months). Ipomœa peltata (weeks or months). Ipomœa turpethum (_nil_ or weeks or months). Ipomœa sp. (7-10 days). Lindenia vitiensis (weeks or months). Maba sp. (7-10 days). Macaranga sp. (1-2 weeks). Melastoma denticulatum. Micromelum minutum. Momordica Charantia (a few days). Morinda Forsteri. Mussænda frondosa. Myristica sp. (3-7 days) Myristica sp. (3-7 days) Myrmecodia sp. Nelitris vitiensis (a few days). Nephelium pinnatum (a few days). Ophiorrhiza leptantha. Phyllanthus sp. Phyllanthus sp. Piper Macgillivrayi. Pittosporum sp. Pleiosmilax vitiensis. Portulaca (lutea?). Portulaca quadrifida. Premna serratifolia. Pritchardia pacifica. Psychotria sp. Psychotria sp. Psychotria sp. Psychotria sp. Psychotria sp. Ptychosperma sp. Rhaphidophora vitiensis. Sapota sp. (a few days) Sapota sp. (a few days) Scævola floribunda. Spondias dulcis (a month). Sterculia sp. (seeds _nil_, fruits months). Stylocoryne sambucina (2 or 3 days). Tabernæmontana (orientalis?) (a few days). Tacca maculata (_nil_ or a few days). Trichospermum Richii (a few days). Urena lobata. Veitchia Joannis. Veitchia sp.

NOTE 5 (page 14).

THE INLAND FIJIAN PLANTS POSSESSING BUOYANT SEEDS OR FRUITS

They come under the following heads:

(a) Plants of the stream-border or the pond-side or of the inland swamp, _e.g._, Lindenia vitiensis and Hydrocotyle asiatica. The extension of the principle by which plants with buoyant seeds or fruits are located, not only at the sea-side but at the water-side generally, is here involved, as explained in Chapter III.

(b) Plants following the rule deduced by Schimper for Terminalia, that when a genus comprises several species possessing buoyant fruits, only those having fruits with the greatest floating power are found at the coast, the least buoyant plants occurring inland; examples, Calophyllum and Guettarda.

(c) Plants that like Ipomœa behave irregularly in respect to seed-buoyancy, a difference in behaviour often associated with varying stations both at the coast and inland.

(d) Plants with dehiscent buoyant capsular fruits, like Sterculia, where dehiscence takes place on the tree and the seeds have no buoyancy. Although the unopened fruit may float a long time, it does not in that condition come under the influence of the currents.

(e) Plants like Citrus Decumana, Gardenia, sp., &c., that, although apparently exceptions to the principle, do not offer much opposition to it, since the first is most at home at the river-side and the second often displays a decided inclination for a station at the coast.

(f) Genuine exceptions to the principle, such as Hibiscus Abelmoschus (see page 21).

NOTE 6 (page 15)

TABLE SHOWING THE DEGREE OF BUOYANCY OF THE SEEDS AND FRUITS OF SOME INLAND HAWAIIAN PLANTS

(Unless otherwise stated, the seeds or fruits sink at once or in a day or two)

Acacia Koa. Aleurites moluccana (1-2 weeks). Alyxia olivæformis. Argemone mexicana. Argyreia tiliæfolia (_nil_ or months). Bidens pilosa. Campylotheca sp. Canavalia galeata. Capparis sandwicensis. Cassia Gaudichaudii. Cassia occidentalis. Cheirodendron Gaudichaudii. Colubrina oppositifolia (weeks). Commelina nudiflora. Coprosma ernodeoides. Coprosma sp. Coprosma sp. Cyathodes Tameiameiæ (a few days). Cyrtandra sp. (a few days). Cyrtandra sp. (a few days). Cyrtandra sp. (a few days). Dianella odorata (a few days). Dracæna aurea. Eclipta alba (months). Erythrina monosperma. Gossypium tomentosum (a week). Gossypium barbadense (a few days). Gossypium sp. cultiv. (a few days). Hibiscus Youngianus (weeks). Hydrocotyle verticillata (weeks). Ipomœa bona nox (_nil_ or months). Ipomœa insularis. Ipomœa pentaphylla. Ipomœa reptans. Ipomœa tuberculata. Jacquemontia sandwicensis. Jussiæa villosa (a few days). Lobeliaceæ (Clermontia). Maba sandwicensis. Metrosideros polymorpha. Mezoneuron kauaiense (pod, a week). Mucuna urens (months). Myoporum sandwicense. Olea sandwicensis, see page 364. Phyllostegia grandiflora. Phyllostegia mollis. Plectronia odorata. Pritchardia Gaudichaudii (5 or 6 weeks). Ricinus communis (7-10 days). Rubus Macraei. Scævola Chamissoniana. Scævola Gaudichaudii. Sida fallax. Sisyrinchium acre. Solanum aculeatissimum. Sophora chrysophylla (pod, 1-2 weeks). Viola Chamissoniana. Waltheria americana.

NOTE 7 (page 15)

SOME INLAND HAWAIIAN PLANTS POSSESSING BUOYANT SEEDS OR FRUITS

Three of these, Eclipta alba, Hibiscus Youngianus, and Hydrocotyle verticillata, frequent wet places, and come under the principle that water-side plants generally have buoyant seeds or fruits. The buoyancy of the seeds of Argyreia tiliæfolia and of Ipomœa bona nox varies with station and may be explained as under Ipomœa in Note 5. The floating power of the fruits of Colubrina oppositifolia may be akin to that of inland species of Terminalia as indicated in Note 5, since another species of the genus C. asiatica, which is a coast plant, has very buoyant seeds. Mucuna urens was no doubt originally, as it now is in tropical America, a littoral plant. The buoyant fruits of Pritchardia Gaudichaudii offer a genuine exception to the principle (see page 330).

NOTE 8 (pages 18, 112)

THE PYRENES OF MORINDA

The pyrenes of the two Malayan inland species of Morinda (M. umbellata and M. longiflora) examined by Professor Schimper do not possess the bladder-like cavity to which those of M. citrifolia owe their floating power, and it is to be inferred from his remarks (p. 183) that they have little or no buoyancy. The pyrenes of a Fijian inland species, near M. Grayi, had no floating power as tested by me, and they lacked the bladder-like cavity.

NOTE 9 (page 18)

THE BUOYANCY OF THE FRUITS OF CALOPHYLLUM

Professor Schimper found that whilst the fruits of Calophyllum inophyllum, the shore tree, remained afloat after 126 days, those of C. amœnum, an inland species, sank in from three to fourteen days, both possessing similar buoyant structures, but to a less degree in the case of the inland species. This genus presents a parallel case to Terminalia referred to on page 17; but the general discussion of the subject will be found in Chapter XIII. According to the above authority C. Calaba, a West Indian coast tree, has buoyant fruits. The same is also true of the fruits of a large inland tree in the Solomon Islands experimented on by me (_Solomon Islands_, p. 305). It would thus appear that the fruits of the genus are as a rule buoyant, and that, as in Terminalia, the least buoyant fruits belong to the inland species. Professor Schimper also shows (p. 182) that the diminished floating power of the fruits of the inland species is associated with diminution in thickness of the buoyant seed-shell which is most developed in the buoyant fruits of the strand species.

NOTE 10 (page 24)

THE BUOYANCY EXPERIMENTS ON BRITISH PLANTS

The experiments in all cases were made to test the floating power of the seed or fruit in the condition in which it is detached from the plant. It usually makes very little difference whether sea-water or fresh water is employed, since in my numerous experiments there were but few exceptions to the general rule that seeds or seed-vessels that sink in fresh water sink also in sea-water. This subject is discussed in Chapter X. However, it may be here observed that the chief effect of the increased density of sea-water is merely to increase the proportion of buoyant seeds or fruits in any particular species.

It is necessary in such experiments to imitate Nature as much as possible. The seed or fruit, as the case may be, must be experimented upon in the condition in which it falls from the plant, or in the condition in which it would be ultimately found in river and pond drift. The seed or fruit should be thoroughly wetted, and air-bubbles removed.

Prolonged drying has but a slight effect on the great majority of seeds and seed-vessels experimented on, and this is just as true of tropical plants. Those that sink at once in the mature and fresh condition rarely float more than a day or two even after drying for a year. The usual effect is to increase the floating capacity of seeds and fruits already buoyant, and not to develop the capacity.

The results given in the table refer only to sound seeds. In fresh-water experiments, in nearly all cases, the seeds ultimately germinate in the water, and this is the usual cause of the close of the experiment. In an ordinary collection of floating seed drift from a pond or river, germination will go on for years at each successive spring, the postponement of germination being a very striking feature with a fair proportion of seeds in river and pond-drift. This subject is dealt with in detail in my paper published in the _Proceedings_ for 1897 of the Royal Physical Society of Edinburgh.

THE TABLE OF RESULTS OF OBSERVATIONS AND EXPERIMENTS ON THE BUOYANCY OF THE SEEDS OR SEED-VESSELS OF MORE THAN 300 BRITISH FLOWERING PLANTS

EXPLANATION OF TABLE.—The capacity of floating for months is thus indicated, ++; of floating for 1 to 4 weeks, +; and where sinking occurs at once or within a week there is no entry. When buoyancy continued in my experiments after 6 and 12 months, it is indicated by Roman numerals (VI and XII). A=an aquatic plant; M=a beach plant; R=a river-side or pond-side plant; var.=variable in floating power.

+--------------------------------------+----+------+ |R Thalictrum flavum | | | |A Ranunculus aquatilis | | | |R Ranunculus hederaceus | | | |R Ranunculus flammula | | | | Ranunculus ficaria | | | |R Ranunculus sceleratus VI | ++ | Var. | | Ranunculus acris | | | | Ranunculus repens XII | ++ | Var. | |R Caltha palustris | + | | | Berberis vulgaris | | | |A Nymphæa alba | | | |A Nuphar luteum | | | | Papaver rhœas | | | | Papaver dubium | | | | Chelidonium majus | | | | Rœmeria hybrida | | | |M Glaucium luteum | | | | Barbarea vulgaris | | | |R Nasturtium officinale | | | |R Nasturtium sylvestre | | | |R Nasturtium amphibium | | | | Arabis hirsuta | | | | Arabis thaliana | | | |R Cardamine pratensis | | | | Cardamine hirsuta | | | | Alliaria officinalis | | | | Brassica campestris | | | | Brassica alba | | | |M Cochlearia officinalis | | | |M Alyssum maritimum | | | | Draba verna | | | | Thlaspi arvense | | | | Capsella bursa pastoris | | | |M Cakile maritima | + | | |M Crambe maritima | + | | |M Raphanus maritimus | + | | | Reseda luteola | | | | Helianthemum vulgare | | | |R Viola palustris | | | | Viola canina | | | | Viola tricolor | | | | Polygala vulgaris | | | | Silene cucubalus | | | |M Silene maritima | | | | Lychnis diurna | | | | Sagina procumbens | | | |M Arenaria peploides (Honckeneya) XII | ++ | | | Mœnchia erecta | | | | Cerastium vulgatum | | | |R Stellaria aquatica | | | | Stellaria media | | | | Stellaria graminea | | | | Stellaria holostea | | | | Spergularia rubra | | | |M Spergularia marina | | | | Spergula arvensis | | | |R Montia fontana | | | |R Elatine hydropiper | | | | Hypericum perforatum | | | | Hypericum quadrangulum | | | |R Hypericum elodes | | | | Linum usitatissimum | | | | Linum angustifolium | | | | Malva rotundifolia | | | | Malva sylvestris | | | | Oxalis acetosella | | | | Oxalis corniculata | | | | Impatiens parviflora | | | |R Impatiens fulva VI | ++ | | | Acer campestre | | | | Ilex aquifolium | | | | Euonymus europæus | + | | | Ulex europæus | | | | Cytisus scoparius | | | | Ononis arvensis | | | | Medicago lupulina | | | | Medicago denticulata | | | | Trifolium incarnatum | | | | Lotus corniculatus | | | | Anthyllis vulneraria | | | | Vicia sativa | | | | Lathyrus pratensis | | | |M Lathyrus maritimus | ++ | | |R Spiræa ulmaria | + | | | Fragaria vesca | | | | Potentilla tormentilla | | | | Potentilla sp. | | | |R Potentilla comarum XII | ++ | | | Alchemilla arvensis | | | | Rosa arvensis | | | | Cratægus oxyacantha | + | | |R Epilobium hirsutum | | | | Epilobium parviflorum | | | |R Lythrum salicaria | | | |R Peplis portula | | | | Bryonia dioica | | | | Cotyledon umbilicus | | | | Saxifraga granulata | | | | Saxifraga tridactylites | | | |R Chrysosplenium alternifolium | | | |R Chrysosplenium oppositifolium | | | | Drosera rotundifolia | + | | |A Myriophyllum spicatum | | | |A Myriophyllum alternifolium | | | |R Hydrocotyle vulgaris XII | ++ | | |M Eryngium maritimum | | | |R Cicuta virosa | ++ | | |R Apium graveolens | | | |R Apium nodiflorum | | | |R Apium inundatum | | | |R Sium latifolium | ++ | | |R Sium angustifolium | ++ | | |R Œnanthe crocata VI | ++ | | |R Œnanthe phellandrium | + | | | Æthusa cynapium | | | |M Crithmum maritimum | ++ | | |R Angelica sylvestris XII | ++ | | |R Peucedanum palustre | ++ | | | Pastinaca sativa | | | | Chærophyllum sylvestre | | | | Smyrnium olusatrum | | | | Hedera helix | | | | Viscum album | | | | Sambucus nigra | | | |R Galium palustre VI | ++ | | | Galium mollugo | | | | Galium aparine | | | | Centranthus ruber | | | | Valerianella olitoria | | | | Eupatorium cannabinum | | | |M Aster tripolium | | | |R Bidens cernua VI | ++ | | |R Bidens tripartita VI | ++ | | | Chrysanthemum segetum | | | | Chrysanthemum leucanthemum | | | | Matricaria inodora | | | |M Matricaria inodora, var. maritima | ++ | | | Matricaria chamomilla | | | | Achillea millefolium | | | | Artemisia vulgaris | | | | Artemisia absinthium | | | | Tussilago farfara | | | | Tussilago petasites | | | | Senecio vulgaris | | | |R Senecio aquaticus | | | |R Senecio palustris | | | | Carduus nutans | | | | Carduus lanceolatus | | | |R Carduus palustris | | | | Carduus arvensis | | | | Tragopogon pratensis | | | | Tragopogon porrifolius | | | | Tragopogon echioides | | | | Leontodon autumnalis | | | | Sonchus oleraceus | | | | Taraxacum dens leonis | | | | Crepis virens | | | | Crepis fœtida | | | | Lapsana communis | | | |A Lobelia Dortmanna | | | |R Hottonia palustris | | | |R Lysimachia vulgaris | + | | |R Lysimachia thyrsiflora | + | | |M Glaux maritima | | | | Anagallis arvensis | | | |M Samolus valerandi | | | | Pinguicula lusitanica | | | | Ligustrum vulgare | | | |R Menyanthes trifoliata | ++ | | |R Limnanthemum nymphæoides | + | | | Convolvulus arvensis | | | | Convolvulus sepium XII | ++ | | |M Convolvulus soldanella XII | ++ | | | Cuscuta europæa | | | | Lithospermum officinale | | | |R Myosotis palustris | | | | Myosotis arvensis | | | | Myosotis versicolor | | | | Lycopsis arvensis | | | | Symphytum officinale | | | | Borago officinalis | | | | Datura stramonium | | | | Solanum dulcamara | | | | Solanum nigrum | | | | Linaria vulgaris | | | | Linaria cymbalaria | | | | Scrophularia nodosa | | | |R Scrophularia aquatica | | | |R Veronica anagallis | | | |R Veronica beccabunga | | | | Veronica agrestis | | | | Veronica arvensis | | | | Bartsia odontites | | | | Rhinanthus crista galli VI | ++ | Var. | |R Pedicularis palustris | ++ | | | Salvia verbenaca | | | |R Lycopus europæus XII | ++ | | |R Mentha aquatica VI | ++ | | | Thymus sp. | | | | Calamintha officinalis | | | | Nepeta glechoma | | | | Nepeta cataria | | | | Prunella vulgaris | | | |R Scutellaria galericulata XII | ++ | | | Stachys betonica | | | | Stachys sylvatica | | | |R Stachys palustris | ++ | | | Stachys arvensis | | | | Galeopsis tetrahit | | | | Ballota nigra | | | | Lamium purpureum | | | | Lamium album | | | | Lamium galeobdolon | | | | Teucrium scorodonia | | | | Ajuga reptans | | | | Verbena officinalis | | | |M Armeria vulgaris | | | | Plantago major | | | | Plantago media | | | | Plantago lanceolata | | | |M Plantago maritima | | | |M Salicornia herbacea | | | |M Salsola kali | + | | |M Suæda fruticosa | | | |M Suæda maritima | | | | Chenopodium album | | | |M Beta maritima | | | | Atriplex patula VI | ++ | | |R Rumex aquaticus | + | | | Rumex crispus | ++ | | | Rumex obtusifolius | | | |R Rumex hydrolapathum XII | ++ | | |R Rumex conglomeratus XII | ++ | | | Polygonum aviculare | | | |M Polygonum maritimum | | | | Polygonum convolvulus | | | |R Polygonum amphibium | | | |R Polygonum persicaria | | | | Polygonum lapathifolium | | | |R Polygonum hydropiper | | | | Euphorbia helioscopia | | | | Euphorbia segetalis | | | |M Euphorbia paralias | ++ | | | Euphorbia peplus (?) | | | | Euphorbia amygdaloides | | | |A Ceratophyllum demersum | | | |A Callitriche aquatica | | | | Urtica dioica | | | | Ulmus campestris | | | |R Alnus glutinosa XII | ++ | | | Betula alba | | | | Corylus avellana | + | | | Quercus robur | + | | | Pinus sylvestris | + | | | Taxus baccata | | | |R Typha latifolia | | | |R Typha angustifolia | | | |R Sparganium ramosum XII | ++ | | |R Sparganium simplex VI | ++ | Var. | |R Sparganium minimum | ++ | | | Arum maculatum | | | |R Calla palustris XII | ++ | | |A Lemna minor | ++ | | |A Lemna gibba | | | |A Naias marina | | | |A Zannichellia palustris | | | |A Ruppia maritima | | | |A Potamogeton natans XII | ++ | | |A Potamogeton oblongus VI | ++ | | |A Potamogeton lucens VI | ++ | | |A Potamogeton perfoliatus | ++ | | |A Potamogeton crispus | | | |A Potamogeton densus | | | |A Potamogeton obtusifolius | | | |A Potamogeton pusillus | | | |R Butomus umbellatus | | | |R Sagittaria sagittifolia VI | ++ | Var. | |R Alisma plantago VI | ++ | Var. | |R Alisma ranunculoides | | | |A Alisma natans | | | |R Damasonium stellatum | | | |R Scheuchzeria palustris | ++ | | |R Triglochin palustre | | | |R Triglochin maritimum | | | |A Hydrocharis morsus ranæ | | | |R Iris pseudacorus XII | ++ | | | Iris fœtidissima | | | | Tamus communis | | | | Fritillaria meleagris | ++ | | | Scilla nutans | | | | Narthecium ossifragum | | | |R Juncus communis | | | | Juncus glaucus | | | |R Juncus articulatus | | | | Juncus squarrosus | | | |R Juncus bufonius | | | |M Juncus maritimus | | | | Luzula campestris | | | |R Cladium mariscus | ++ | | |R Blysmus rufus | ++ | | |R Scirpus palustris | | | |A Scirpus fluitans | | | | Scirpus setaceus | | | | Scirpus holoschœnus | | | |R Scirpus lacustris | | | |M Scirpus maritimus | + | | | Scirpus sylvaticus | | | | Eriophorum alpinum | | | | Eriophorum vaginatum | | | | Eriophorum polystachion | | | |R Carex leporina | ++ | | | Carex stellulata XII | ++ | | |R Carex canescens | ++ | | | Carex remota XII | ++ | | |R Carex paniculata XII | ++ | | |R Carex vulpina XII | ++ | | |R Carex acuta VI | ++ | | | Carex hirta | | | |R Carex flava VI | ++ | Var. | | Carex distans | | | | Carex panicea | | | |R Carex pseudocyperus VI | ++ | | |R Carex ampullacea | + | | |R Carex paludosa XII | ++ | | | Carex sp. | | | | Carex sp. | | | |R Leersia oryzoides | | | |R Alopecurus geniculatus | | | | Agrostis sp. | | | | Agrostis sp. | | | |R Poa aquatica | | | |R Poa fluitans | | | | Melica nutans | | | |R Arundo phragmites | +? | | +--------------------------------------+----+------+

Total of the original list: 320 species belonging to 192 genera and 65 families. Of these, about 260 were tested by the author, the data for the remaining species being mainly derived from the writings of Thuret, Kolpin-Ravn, and Sernander, with a few from those of Darwin and Martins.

NOTE.—Whilst this work has been going through the press, the author has added thirteen species, seven genera, and two families to the list above given; but the general inferences are not affected by the additions. The corrected total would, therefore, be 333 species, 199 genera, and 67 families.

_On the effect of drying on the buoyancy of seeds and seed-vessels_

It has been already observed that this is as a rule but slight, and that in the great majority of cases the effect of prolonged drying for many months, or even for years, is at the most to give a seed or fruit originally non-buoyant a floating power of a few days’ duration. This is a subject to which I have paid especial attention in my experiments, since, of course, much depends on it in the way of dispersal by currents. It is obvious that a seed or fruit possessing impermeable coverings at the time of its separation from the parent can scarcely be compared with one where the coverings only attain their water-proof capacity by drying. Most gardeners know that seeds which dry easily take up moisture easily, and the principle applies in a varying degree to the great majority of seeds and fruits.

Darwin was inclined to attach importance to adventitious buoyancy acquired by drying; and in the _Origin of Species_ he refers to instances offered by the fruits of the Hazel (Corylus), the Asparagus, and Heliosciadium. In Note 48 I have referred to the cases of the Oak and the Hazel; and, indeed, we have only to examine the beach-drift in various parts of the world, and to look at their respective stations, to learn that this is not an effective mode of dispersal. Buoyancy of seed or fruit is only one of many other qualities that is concerned with distribution by currents. Nature does not act in this way in seed-distribution, and there can be little doubt that the author of the _Origin of Species_ would have been the first to abandon this view, if his researches had been continued. It should be especially noted that plants of the sea-beach, where the floating power happens to be _nil_, or limited only to a week or two, would have derived great advantage from the drying of their seeds or fruits if it was really effective in aiding dispersal by currents. However, with plants like Cakile maritima, Eryngium maritimum, Glaucium luteum, &c., the effect of drying is very small.

NOTE 11 (page 25)

THE EFFECT OF SEA-WATER IMMERSION ON THE GERMINATING CAPACITY OF SEEDS AND SEED-VESSELS

Berkeley, Darwin, Martins, and others, long ago established the capacity of seeds to germinate after prolonged immersion in sea-water. The reader will find a _resumé_ of their results in the appendix to Mr Hemsley’s volume on the _Botany of the Challenger Expedition_. The subject is well illustrated in the original papers of those authors, and in my later papers on the flora of Keeling Atoll, and on the seed-drift of the Thames.

I may here remark that the earlier observers often pay more attention to the retention of the germinating capacity after sea-water immersion than to the degree of buoyancy. For this reason I have not been able to make great use of the buoyancy results of Martins, since he frequently does not distinguish between temporary and long-sustained buoyancy, an objection also pointed out by Thuret and Hemsley.

NOTE 12 (page 27)

THE BUOYANCY OF THE FRUITS OF GALIUM APARINE

Norman and Sernander (see p. 172) attribute considerable buoyancy to these fruits on account of the hollow cavity in each. I used to find them in England in floating river-drift in autumn; and Norman observed them on the Scandinavian beaches. They do not, however, float long, as the cavity is open; and in two sets of my experiments they sank within a few days.

NOTE 13 (page 29)

THE BUOYANCY OF THE SEEDS OF CONVOLVULUS SEPIUM

This plant seeded freely in 1893 in the Lower Thames Valley, as at Molesey. I kept some of the seeds afloat for thirty-three months, of which the first nine months were spent in sea-water and the rest in fresh-water. One seed, at the end of the period, germinated healthily in the fresh-water.

NOTE 14 (page 26)

OTHER LONG FLOTATION EXPERIMENTS

Whilst keeping my collections of Thames seed-drift in water from year to year, I obtained a number of records of long “flotations.” Thus in several cases, as with Bidens cernua and different species of Carex, germination of the floating fruit took place in the water after a period of two years. The same is also true of the seeds of Iris pseudacorus and of the drupes of Sparganium ramosum. The last-named remained afloat in the vessels, with the seed still sound, after four years; and the fruits of Carex paludosa germinated afloat after three years in water. Many drift fruits and seeds did not germinate freely in the vessels until the second spring, that is, after a lapse of eighteen months; and in those cases where the experiments were still further prolonged, a few germinated in the vessels in the third and sometimes even in the fourth year.

NOTE 15 (pages 33, 280)

THE OCCURRENCE INLAND OF SILENE MARITIMA

Prof. Schimper appeared to be in doubt as to the inclusion of this littoral plant amongst those found in elevated mountain districts. However, an interesting note on the occurrence of this plant on the summit of one of the inland Norwegian mountains is given by Sernander (p. 405), and is referred to by me on page 280 of this work.

NOTE 16 (page 34)

THE BUOYANCY OF THE SEEDS OR FRUITS OF THE BRITISH BEACH-PLANTS THAT ALSO OCCUR INLAND

My experiments in the case of Armeria vulgaris, Artemisia, Cochlearia officinalis, Plantago, the maritime forms of Spergularia rubra with and without winged seeds, and Silene maritima disclose little or no floating capacity even after prolonged drying. Thuret obtained similar results for the Spergularia. It is unlikely that other plants of the group possess any floating power worth speaking of. As indicated in Note 71, the fruits of Raphanus maritimus float only for 7 to 10 days.

Nature disperses the fruits of Armeria vulgaris inclosed in the persistent calyx; but in this condition they float only for 2 to 4 days in sea-water, and the buoyancy of the capsule and seed is still more limited. They are sufficiently light to be blown some distance by strong winds, and the stiff hairs would cause them to adhere to a bird’s plumage in the case of gulls nesting where the plants grow.

Reference to Matricaria inodora is made under Note 18.

NOTE 17 (page 35)

THE BUOYANCY OF THE SEEDS OR FRUITS OF THE GROUP OF BRITISH LITTORAL PLANTS THAT FREQUENT SALT MARSHES AND MUDDY SHORES

_Aster tripolium._ The achenes, with or without the pappus, sink in fresh and salt water in a day or two even after a year’s drying.

_Glaux maritima_ } _Plantago maritima_ } The small seeds, or the seed-like nucules as _Samolus valerandi_ } in Suæda, have but little floating power _Suæda fruticosa_ } even after prolonged drying. _Suæda maritima_ }

_Salicornia herbacea._ Would be dispersed probably by floating portions of the plant, which, however, soon break down and the liberated seeds sink. The floating seedling thrives in sea-water and could be carried great distances (see Note 19).

_Salsola kali._ I experimented on this plant, both on the coast of Devonshire and in Chile, with the same results in both localities whether in the fresh state or after drying for weeks. The fruit sinks, but when the plant dries the fruit is often detached inclosed in the perianth, and floats in that condition in sea-water for a few days. Portions of the plant of various sizes bearing mature fruits all sank within ten days. It would seem at first sight, from the observations of Prof. Martins, that the fruits float for several weeks; but his experiments were mainly directed to testing the powers of germination after sea-water _immersion_; and it is often not at all clear whether _flotation_ is implied or even to be correctly inferred. There is a slight suspicion of germination on the plant. Sea-birds doubtless aid in the dispersion of this plant; the dry crisp portions of the plant carrying fruits catch readily in one’s clothes on account of the prickly-pointed leaves.

_Scirpus maritimus._ The fresh fruits float a few weeks in sea-water in most cases, but 10 per cent. remain afloat after two months. After drying for some months 30 per cent. remain floating after two months’ immersion.

} The fruits float a few days or a week. Drying _Triglochin maritimum_ } somewhat increases the buoyancy. Sir W. _Triglochin palustre_ } Buller in New Zealand found in the gullet } of Anas superciliosa, the Grey Duck, numbers } of the fruits of Triglochin triandrum.

NOTE 18 (page 35)

THE BUOYANCY OF THE SEEDS OR FRUITS OF THE BRITISH LITTORAL PLANTS THAT ARE CONFINED TO THE BEACH

_Arenaria (Honckeneya) peploides._ The seeds float for many months in sea-water unharmed, 75 per cent. floating after a year. They never germinate in sea-water; but on being transferred to fresh water after many months in sea-water they germinate healthily in a few days. These seeds only float a few days in fresh water, all sinking within 10 days, and even after a year’s drying they sink in a week or two. Precisely the same results were produced in my experiments in 1892 on Cornish seeds, and in 1904 on Devonshire seeds. In the great contrast between their floating capacity in sea-water and in fresh water the seeds of this plant defy the general rule that seeds that float a long time in sea-water float also a long time in fresh-water. According also to Sernander the seeds float a long time in the sea. He says that the capsules float, but since they ultimately dehisce this could scarcely be efficacious in dispersal. Floating portions of the plant also aid in its dispersal, according to the same authority (p. 174). The plant forms great extended masses on the pebbly shores of Spitzbergen (Ekstam, p. 28).

_Beta maritima._ Thuret found that the dried fruits of this plant floated only two or three days in sea-water; whilst in my sea-water experiments the freshly gathered fruits floated only one or two days. Sernander speaks of them as fitted for dispersal from shore to shore; but this could only be to a limited extent. Martins and Thuret established by experiment the capacity of the germination of seeds of other species of Beta after long immersion in sea-water; and the first seems to imply that those of Beta vulgaris float for many weeks; but I am inclined to think an error lies here.

_Cakile maritima._ The fruits, even after long drying, float, as a rule, only a week and sink within ten days, the same results being afforded in my sea-water experiments in 1893 on fruits from Cornwall, and in 1904 on fruits from Devonshire. The fruits are common in the stranded drift on the north coast of Devonshire and may often be seen germinating there. They are also frequent in the beach drift of the Scandinavian coasts (Sernander, p. 156).

_Crambe maritima._ The fruits were kept floating by Sernander more than 13 days (p. 165). Martins implies that they floated for 45 days. Darwin says that they germinated after 37 days’ immersion in sea-water, but does not specify that they floated all the time.

_Crithmum maritimum._ The ripe fruits readily separate into the two carpels, which are very buoyant and float in sea-water for months. In my experiments, 95 per cent. remained afloat after 10 months. It is remarkable that whilst in sea-water the spongy covering of the carpels retains its vitality, in fresh-water it becomes sickly and decays and the carpels lose their floating power, so that they float weeks instead of months as in the sea-water. The carpels are extremely light, being washed up in the spray and blown up by the wind amongst the lightest of the stranded drift of the Devonshire beaches. In a moderate gale they are often blown off the beach and up the cliff-faces.

_Convolvulus soldanella._ From 40 to 50 per cent. of the seeds float after six months in sea-water, and about 30 per cent. float after eighteen months, retaining up to the end their germinating capacity. Sernander implies that the plant is not found on the Scandinavian coast to the north of Nissum Fjord in Denmark. It is known, however, to occur in the south of Scotland. (I am indebted to Mr. Millett for his extremely kind assistance in experimenting on this plant about ten years since.)

_Eryngium maritimum._ The fruits float in sea-water, as a rule, only 3 or 4 days and all sink within a week. After drying for three months, the floating period is only increased by a day or two. Though not at all suited for transport for any distance by the currents, the carpels, on account of their long prickly calyx teeth, would readily become entangled in a bird’s plumage, and doubtless they are dispersed usually in that fashion.

_Euphorbia paralias._ The seeds float a long time unharmed in the sea. In my experiments at least 90 per cent. remained afloat after six weeks in sea-water. On account of their small size they are liable to be overlooked in beach drift; but they are to be found stranded on the sands of our southern coasts, and they came under my notice in abundance in the seed-drift of the Sicilian beaches.

_Glaucium luteum._—The seeds have no proper buoyancy even after prolonged drying. On account of their oiliness they will float at first on still water; but they can be made to sink at once or in a day by dropping water upon them. The mode of dispersal is problematical.

_Lathyrus maritimus._—The seeds are evidently able to float a long time. They were, according to Sernander (p. 178), found in quantities by J. Schmidt cast up on some sand-islets near Falster in Denmark; and the plant is regarded by Norman as distributed over the coasts of Arctic Norway through the agency of the currents. They have, as observed by Schmidt, considerable floating powers. Some small leguminous seeds, seemingly of this species, which I found in the beach drift of Woollacombe Sands, Devonshire, floated uninjured for many weeks in sea-water.

_Matricaria maritima,_ maritime variety of M. inodora. The fruits floated in my experiments unharmed after eight months in sea-water. In an experiment made some years since on the fruits of the inland form I noted that they had little or no buoyancy; but it is necessary to repeat the observation. Sernander (p. 181) supports Norman’s view that these plants are spread by the currents in Arctic Norway. The fruits occur in the Baltic sea-drift and also in fresh-water drift. M. inodora is found on sandy beaches in Nova Zembla. I am inclined to regard the maritime form from the dispersal standpoint as a distinct species.

_Polygonum maritimum._—I have made observations on this plant in Devonshire, the Lipari Islands, and the coast of Chile. As in the case of several other species of Polygonum tested by me the fruits have little or no buoyancy, but inclosed in the perianth they float three or four days. The entire plant floats; but portions placed in sea-water sank within five or six days. Shore-birds can alone explain the wide distribution of this species.

The structural characters of some of these fruits or seeds are in their relation to buoyancy discussed on page 115. It may be here observed that the valuable results obtained by Prof. Martins in testing the germinating capacity of the fruits and seeds of several of the shore-plants above mentioned, after long immersion in sea-water, are at times not to be depended on for the flotation indications, the persistence of the seed’s vitality being the special purpose of his research. His negative results as regards germination are not, however, always conclusive, since the period employed from April to June was quite insufficient. In many of my experiments seeds after long flotation in sea-water did not germinate for a year or more afterwards. If his investigation had been extended, the opinion that the Ranunculaceæ, the Malvaceæ, and the Convolvulaceæ are apparently least able to resist the action of sea-water would never have been formed. A very large amount of evidence now shows that most seeds or fruits that are at all well protected will germinate after long immersion in sea-water. But all experiments must be well safeguarded and extended over a year or two. The necessity of this was long since shown by Thuret. By employing double sets of seeds he ascertained that in a third of the species germination failed not only in the case of the seeds immersed in sea-water, but also in those that had not been placed in sea-water at all. Future investigators may, however, regard the buoyant qualities of seeds or fruits with their associated structural characters as offering now the true line of research. Observers beginning with Berkeley and Darwin down to the present time have quite established the fact that seeds as a rule germinate freely after long sea-water immersion.

NOTE 19 (page 35)

ON GERMINATION IN SEA-WATER

During my experiments on the buoyancy of about 270 British plants, about a fourth of them (including most of those with buoyant seeds or fruits) were subjected to prolonged immersion in sea-water from periods varying from six to thirty-three months. If we except plants like Aster tripolium, Salicornia herbacea, Triglochin maritimum, &c., that live normally in salt marshes, or on the muddy banks of estuaries, only one of the whole number, namely, Ranunculus sceleratus, displayed the capacity of germination in sea-water. Amongst the plants that failed may be mentioned the following that are confined to the sea-beach—Arenaria peploides, Cakile maritima, Convolvulus soldanella, Eryngium maritimum, Euphorbia paralias, Glaucium luteum, and we may here include Crithmum maritimum of the rocky coasts. Of the beach-plants that also grow inland, Silene maritima and Spergularia rubra (excepting the form found on muddy coast flats) likewise failed. Amongst the plants of miscellaneous inland stations that failed were Atriplex patula, Bidens cernua, B. tripartita, Calla palustris, several species of Carex both from dry and wet situations, Convolvulus arvensis, C. sepium, Hydrocotyle vulgaris, Iris pseudacorus, several species of Juncus, Lycopus europæus, Mentha aquatica, Ranunculus repens, Rhinanthus crista galli, several species of Rumex, Scutellaria galericulata, Sparganium ramosum, &c.

In nearly all the plants that failed to germinate in sea-water the capacity of readily germinating in fresh water was displayed. The restraining power of immersion in sea-water was illustrated over and over again in my experiments. During the course of an experiment seeds removed from the sea-water vessel and placed directly in a vessel of fresh water kept beside the other germinated in a few days, whilst those left in the sea-water never germinated, though often kept there for months after. It was also noticeable that a previous sea-water immersion favoured early germination in fresh water. It may be added that most of the experiments were on floating seeds and seedvessels, though germination also occurred in the sunken state.

It was ascertained in the exceptional case of Ranunculus sceleratus, that although germination took place in sea-water, it was only after a prolonged soaking of months had prepared the way. Of a number of its seed-like fruits placed in fresh water and in sea-water in April and kept under the same conditions, those in fresh water germinated freely in a week or two, whilst those in sea-water did not begin to germinate until the following October. Whilst the floating seedlings produced by germination in fresh water grew vigorously and developed roots, those resulting from germination in sea-water and left in the vessel only attained a length of four millimetres in two months, developed no roots, and showed only the first leaf. The sea-water seedlings were pale green, and in their stout fleshy appearance contrasted greatly with the slender fresh-water seedlings.

With regard to the germination in sea-water of the plants of the salt marsh and of the mud-flats of estuaries, the following observations may be made. With Aster tripolium the seeds germinate readily in sea-water even when its density is raised by evaporation to 1·040; and I think that by a carefully graduated series of experiments they could be induced to germinate in brine. The seeds of Salicornia herbacea germinate in sea-water more readily than in fresh water; and the sea-water seedling is much the more vigorous and healthy of the two. I kept the floating seedlings in sea-water for about ten weeks from the date of germination, when they had developed the second joint and were throwing out rootlets. After that, unless placed in salt-mud, they became sickly and died. The floating seedling can evidently disperse the species. I found with Spergularia marina, the maritime form of S. rubra, that seeds of the plants growing on a sandy beach did not germinate in sea-water, only those from plants growing on muddy coast-flats doing so. But the sea-water seedlings, unlike those of Salicornia herbacea, but like those of Ranunculus sceleratus, when left in sea-water did not thrive. The seeds of Triglochin maritimum, as well as those of T. palustre, behave very similarly in sea-water, germinating readily, the liberated seedlings thriving afloat and producing the plumule. The ultimate test of the capacity for germinating in sea-water seems to lie in the behaviour of the seedling when left in the sea-water. Unless it belongs to a characteristic plant of the salt marsh or of the estuary, like Salicornia, it makes but little attempt at growth whilst afloat in sea-water, showing no rootlets, though at times developing the plumule.

The germination of seeds in sea-water also attracted the notice of Darwin; but his results in some respects are scarcely those I should have looked for (_Gardener’s Chronicle_, May, 1855, and _Journ. Linn. Soc._, vol. i., p. 130, 1857). Out of the seeds of 87 plants placed in sea-water to test their capacity of germination when afterwards planted, in three cases, those of Tussilago farfara, Convolvulus tricolor, and the garden Orache (Atriplex), the seeds germinated under the water, the freed seedlings, as with the two first named plants, living in the sea-water for some time after. Darwin was evidently himself surprised at these results, and I am quite unable to understand them. In England and in the tropics I have carried on prolonged sea-water experiments on the seeds of at least fifteen species of Convolvulus and Ipomœa (including the beach plants C. soldanella and I. pes capræ) and have never obtained such a result. The seeds will nearly always germinate well in fresh water; but in sea-water the process begins, as indicated by the swollen seed, and then aborts, the embryo dying (see page 83). The seeds of Atriplex patula, though a long time in sea-water in my experiments, made no attempt to germinate there. Neither Prof. Martins, who experimented upon the effects of sea-water immersion on the seeds of nearly 100 plants, including many coast species, nor M. Thuret, who experimented in sea-water on the seeds of 251 plants, the experiments being in some cases prolonged for more than a year, make any reference, as far as I could gather from their writings, to any cases of germination in sea-water. Darwin’s results, however, are always significant in matters of dispersal; and perhaps one of my readers will be able to experiment again on his three plants.

When in Hawaii, I made some observations on the germination of Batis maritima in sea-water, a plan with which I was also familiar in its home in the salt-water pools of the coast of Peru. The mature fruits, on being freed from the parent plant in sea-water, float away, and in from one to two weeks they break down from decay, setting free the seeds. The seeds float in sea-water indefinitely, their buoyancy only terminating with their germination, the first seeds germinating afloat about six weeks after the breaking down of the fruit, whilst the rest continue to float in the sea-water during the next three months, some of them germinating at intervals, and all of them doing so eventually. Strange to say, although the seedlings remained healthy whilst afloat in the sea-water, they made no effort either to separate the cotyledons or to produce a plumule.

NOTE 20 (page 42).

ON THE MAXIMUM HEIGHTS REACHED BY SOME SHORE PLANTS IN THEIR EXTENSION INLAND IN VANUA LEVU, FIJI

Since they occupy the “talasinga” districts described in the following note, these shore plants would be expected to extend as high as those districts extend, namely, to about 1,500 feet above the sea. This indeed represents their limit excepting in one instance; but many fall considerably short of this elevation.

_Canavalia obtusifolia_, variety, 700 feet, rare. _Cassytha filiformis_, 950 feet. _Cerbera Odollam_, 1,200 feet: 2,600 feet in one exceptional case on the slopes of Mbatini. _Colubrina asiatica_, 400 feet. _Cycas circinalis_, 1,100 feet. _Derris uliginosa_, 1,000 feet, rare. _Ipomœa pes capræ_, 1,300 feet. _Morinda citrifolia_, 700 feet. _Scævola Kœnigii_, not common inland, and rarely over 100 feet above the sea; but it may occur miles from the beach, as near Vatu Levoni, where a few stunted plants were growing five miles from the coast. _Vitex trifolia_, 1,300 feet, usually more or less unifoliolate and procumbent.

Unless otherwise stated all the plants above named are common inland, as also are _Premna tahitensis_, _Tacca pinnatifida_, _Tephrosia piscatoria_, _Hibiscus tiliaceus_, &c.; but I have made no note of _Thespesia populnea_ occurring far off the beach.

NOTE 21 (pages 42, 43)

ON THE DWARFING OF SHORE PLANTS WHEN EXTENDING INLAND INTO THE “TALASINGA” PLAINS IN VANUA LEVU.

_Premna tahitensis_, 9 or 10 feet high at the coast, may here be only 3 feet high. Other trees like _Morinda citrifolia_ become also stunted. _Cerbera Odollam_, a moderate-sized tree at the coast, may in the “talasinga” plains be only 4 to 6 feet high, but it here displays distinct varietal characters. Whilst the shore trees of Cerbera Odollam have broad leaves (length 3 times the breadth) with obtuse points, and short, stout flower-peduncles (1-1/2 - 2 inches), the inland or “talasinga” species has long lanceolate leaves (length 7 or 8 times the breadth), and long, slender flower peduncles (3 inches). However, intermediate forms are common, the broad-leaved coast tree approaching the inland plant and _vice versâ_.

NOTE 22 (page 43)

THE “TALASINGA” PLAINS OF VANUA LEVU, FIJI

Amongst the most conspicuous features of the north and north-west or lee sides of the large islands of Vanua Levu and Viti Levu are the extensive rolling plains that extend from the sea-border for some miles inland to the foot of the mountains. It is to those of the first-named island that the following remarks strictly apply; but no doubt they will serve equally well for those of the other island. In the first volume on the geology of Vanua Levu, reference is frequently made to this subject, and the reader may profitably look at the remarks there made.

Here the mountain-forests more or less abruptly cease, and we have an undulating region of grass, reeds, and ferns dotted over with Casuarinas, Pandanus trees, Cycads, Acacias, and shrubby growths. Though the list of plants characteristic of these plains is not small, they are not, as a rule, numerous in any one locality, and the general appearance is one of aridity. A dry, crumbling soil, often deeply stained by iron-oxide, is plentifully exposed; and blocks of basic volcanic rocks in all stages of disintegration are strewn over the surface in many localities. Rivers, fed by the heavy rainfall of the forested slopes of the mountains, traverse these regions, but, as a rule, receive no tributaries; and the districts have, in fact, well earned the name given to them by the natives of the “talasinga,” or sun-burnt, lands.

The vegetation, though sparse and scanty in comparison with that of the forests, is sufficiently varied when it comes to be more closely examined. In one locality we may have extensive tracts covered with Gleichenia, Pteris, and other ferns of the bracken habit. In another, tall reeds (Eulalia) and grasses cover large areas. Here, more than one species of Tacca (T. pinnatifida and T. maculata) thrive. There, the Turmeric (Curcuma longa) abounds. Trailing over the soil in one place we notice Ipomœa pes capræ, in another the Yaka (Pachyrrhizus trilobus), and in another the procumbent unifoliolate form of Vitex trifolia. Amongst the shrubs and small trees we observe in different localities the Sama (Commersonia echinata), the Mbulei (Alstonia plumosa—one of the rubber plants), Mussænda frondosa, Melastoma denticulatum, and Nelitris vitiensis, the Nunga-nunga. Dodonæa viscosa, found in similar regions in Australia and New Zealand, abounds in places; and here and there may be seen species of Hibbertia, another Australian genus. Fagræa Berteriana, the Mbua tree, grows abundantly in certain districts, as in the Mbua plains, and Gardenias are at times abundant. One or two characteristic beach-plants have been already mentioned, and amongst others particularly frequent in these plains are Cassytha filiformis, Cerbera Odollam, Morinda citrifolia, and Premna tahitensis.

When these talasinga districts approach the forests, patches of wood occur at intervals, and we observe here the Candle-nut Tree (Aleurites moluccana), the Vunga (Metrosideros polymorpha), and the Thau-kuro (Casuarina nodiflora). Such are some of the botanical features of these districts; but the reader will acquire a sufficiently correct general notion of the floral physiognomy of these regions if he bears in mind their most conspicuous characters, those of an undulating region more or less covered with ferns, tall reeds, and grass, and dotted over, either separately or in clumps, with Casuarinas (C. equisetifolia), Screw-pines (Pandanus odoratissimus), Cycads (C. circinalis), and Acacias (A. Richii, &c.).

However, the peculiar vegetation of these plains often ascends the lower slopes of the mountains, reaching to various elevations. In Vanua Levu it often ceases at 900 or 1,000 feet, but it may only reach to 400 or 500 feet, and, on the other hand, not uncommonly it ascends to as much as 1,500 feet, the greatest elevation recorded by me being 1,600-1,700 feet in the Sealevu district. It extends miles inland, and where conditions are suitable it may reach the heart of the island.

Different explanations have been offered of the origin of the peculiar vegetation of the leeward slopes of these islands. It is, however, a phenomenon that is presented over much of the globe by islands lying in the track of regular winds, the weather, or wet, side being densely wooded, whilst the lee, or dry, side is covered with grass, ferns, and similar vegetation. The predisposing cause must be climatic; and although Mr. Horne’s explanation attributing it to the effect of fires and to a faulty system of native cultivation (pp. 80, 132) may be doubtless true in certain localities, the influences at work here must be the same as are at work in other islands and on continental coasts in other parts of the world.

But for all that it is not easy to give a definite explanation even from a meteorological standpoint. Those who are interested in this subject will recall the desert districts of Australia and the dreary sandy wastes of the coast of Northern Chile and Peru; and they will be cautious in venturing on a definite explanation even with such relatively unimportant examples of the same principle as are exhibited by the islands of Fiji. Dr. Seemann, writing of these “talasinga” plains (p. xii), remarks that “their very aspect is proof that rain falls in only limited quantity,” the mountainous backbone of the islands intercepting, as he holds, much of the rainfall. But the subsequent observations of Mr. Holmes, at Delanasau, in the “talasinga” district on the north-west side of Vanua Levu, have shown that there is by no means a small rainfall in this locality, the average rainfall, for instance, for the seven years ending December, 1877, being 113 inches, which must be quite two-thirds or three-fourths of the fall on the weather side of the island (see p. 215); whilst the average number of days on which rain fell was 156. The true cause would seem to lie in the excessive dryness of the air on the lee side of the islands between the rains, and the whole matter may, perhaps, be one rather for the hygrometer than for the rain-gauge. I have no comparative data bearing on this point; but Mr. Holmes, whose observations as here quoted are from Horne’s _Year in Fiji_, found that the mean relative humidity for 1875 at 1 P.M. was 63, which is certainly very low for the tropics. I may remark that, as far as personal experience goes, the climate on the lee side of Vanua Levu is much more enervating, much less healthy, and the air is far more “drying” than on the side exposed to the trade-wind.

Geological characters, as I found, explained nothing in this connection, the “talasinga” vegetation sometimes occurring on basaltic areas, at other times on the “soapstone” or calcareous mud-stone, and again on coarser tufaceous rocks. In my volume on the geology of Vanua Levu (p. 57), it is pointed out that the extensive disintegration of the basaltic rocks, that are exposed on these plains in places, affords evidence of the great antiquity of these “talasinga” districts in their present unforested condition. The extent to which these rocks have weathered downward is remarkable. In some places they are decomposed to a depth of ten feet and more. The same inference is to be drawn from the occurrence of fragments of limonite, or bog-iron ore, over these plains, marking as they do original swampy tracts that, with a few exceptions, have long since disappeared. Such deposits indicate that these plains have been for ages in the same condition. ... It may be added that, according to Mr. Lister and Mr. Crosby, the features of the “talasinga” plains occur in the Tongan Group on the leeward sides of the islands of Eua and Vavau.

NOTE 23 (page 43)

SCHIMPER’S GROUPING OF THE INDO-MALAYAN STRAND-FLORA

It is divided into four formations—the Mangrove, the Nipa, the Barringtonia, and the Pes-capræ. The two last make up my Beach-formation, the Barringtonia formation comprising the trees, shrubs, &c., immediately lining the beach, and the Pes capræ including the creepers and bushes of the beach itself. In the Pacific islands it is not always easy to preserve this distinction. The Nipa formation corresponds in some respects with my Intermediate or Transition formation, lying as it does between the mangrove-belts and the woods of the interior; but the swamp-palm (Nipa fruticans) that forms it in the mass is not found in Fiji or, indeed, in the Pacific islands, excepting the Solomon and Caroline Groups.

NOTE 24 (page 44)

GROUPING OF SOME OF THE CHARACTERISTIC PLANTS OF THE STRAND-FLORA OF FIJI

(a) _Beach-formation._—Calophyllum inophyllum, Thespesia populnea, Triumfetta procumbens, Carapa moluccensis, Canavalia obtusifolia, Vigna lutea, Pongamia glabra, Sophora tomentosa, Cæsalpinia Bonducella, Acacia laurifolia, Barringtonia speciosa, Terminalia Katappa, Gyrocarpus Jacquini, Pemphis acidula, Morinda citrifolia, Guettarda speciosa, Wedelia biflora, Scævola Kœnigii, Cordia subcordata, Tournefortia argentea, Ipomœa pes capræ, Cassytha filiformis, Hernandia peltata, Pandanus odoratissimus, &c.

(b) _Mangrove-formation._—Carapa obovata, Rhizophora mucronata, Rhizophora mangle, Bruguiera Rheedii, Lumnitzera coccinea, Scirpodendron costatum, &c. (See below.)

(c) _Intermediate or Transition-formation._—Hibiscus tiliaceus, Heritiera littoralis, Smythea pacifica, Derris uliginosa, Entada scandens, Barringtonia racemosa, Cerbera Odollam, Clerodendron inerme, Vitex trifolia, Excæcaria Agallocha, &c.

N.B.—It is not possible to draw a definite line between the plants of the mangrove swamp and those of the tracts around. Several of the plants placed in the intermediate formation, such as Heritiera littoralis, Entada scandens, Excæcaria Agallocha, &c., are just as much at home amongst the mangroves. In the same way it is often difficult to distinguish between the Beach and the Intermediate formations, and plants like Cerbera Odollam, Hibiscus tiliaceus, and Vitex trifolia belong equally to both.

NOTE 25 (page 47)

THE STRAND-FLORA OF THE TAHITIAN REGION

Drake del Castillo’s _Flore de la Polynésie française_ deals mainly with the Society or Tahitian Islands, but also with the Marquesas, Paumotus, Gambier Islands, and Wallis Island. The last-named, however, lies in Western Polynesia, and is not dealt with in this connection. There is no reason to believe, judging from the general character of the islands and from Cheeseman’s memoir on the Rarotongan flora, that the strand-plants of the islands of the Cook and Austral Groups, which also belong to this region, differ materially from those of the Tahitian islands proper. Rarotonga, however, possesses Entada scandens, not recorded as a growing plant from any other part of East Polynesia, excepting perhaps Mangaia in the same group.

NOTE 26 (page 48)

THE FIJIAN SHORE-PLANTS NOT FOUND IN TAHITI

Although most of these plants, such as Barringtonia racemosa, Clerodendron inerme, Entada scandens, Excæcaria Agallocha, Heritiera littoralis, Smythea pacifica, &c., have fruits that float for months, and could have reached Tahiti as readily as some of the beach-plants that have successfully established themselves, there are a few like Dalbergia monosperma, Derris uliginosa, and Scirpodendron costatum, the fruits of which only float for weeks, and it is possible that they may have been unable to reach there.

NOTE 27 (page 49)

THE INTRUDERS INTO THE BEACH-FLORA FROM THE INLAND PLANTS OF TAHITI

Drake del Castillo mentions several, such as species of Boerhaavia, that could only be occasional intruders; but it is noteworthy that Gardenia tahitensis appears to be a genuine recruit from inland. The xerophilous habit of the Pacific Gardenias and their station, usually near the coast, however, would render this possible.

NOTE 28 (page 52)

THE LITTORAL PLANTS OF THE HAWAIIAN ISLANDS

Column headings:

A: Indigenous. B: By aborigines in ancient times. C: By Europeans soon after discovery. D: Old World. E: New Worlds. F: Both Worlds. G: Large. H: Small. I: Float for months. J: Sink at once or in a few days. K: Attract frugivorous birds.

+---------------------------+---+---+---+---+---+---+---------------------+ | | Origin. | Distri- | Characters of fruit | | | | bution. | or seed. | | +---+---+---+---+---+---+-------+---------+---+ | Species.[5] | |Intro- | | | | Size. |Buoyancy.| | | | |duced. | | | | [6] | | | | | +---+---+ | | +---+---+-----+---+---+ | | A | B | C | D | E | F | G | H | I | J | K | +---------------------------+---+---+---+---+---+---+---+---+-----+---+---+ | Acacia Farnesiana |...|...| + |...|...| + |...| + |weeks|...| ? | | Cæsalpinia Bonducella | + |...|...|...|...| + |...| + | ... | + |...| | Calophyllum inophyllum |...| + |...| + |...|...| + |...| + |...|...| | Cassytha filiformis | + |...|...|...|...| + |...| + | + |...| + | | Colubrina asiatica | + |...|...| + |...|...|...| + | + |...|...| | Cordia subcordata |...| + |...| + |...|...|...| + | + |...|...| |E Cuscuta sandwichiana | + |...|...|...|...|...|...| + | ... | + |...| | Cocos nucifera |...| + |...|...|...| + | + |...| + |...|...| |P Gossypium tomentosum | + |...|...|...|...|...|...| + | ... | + |...| |P Heliotropium anomalum | + |...|...|...|...|...|...| + | ... | + |...| | Heliotropium curassavicum| + |...|...|...|...| + |...| + | ... | + |...| | Herpestis Monnieria | + |...|...|...|...| + |...| + | ... | + |...| | Hibiscus tiliaceus |...| + |...|...|...| + |...| + | + |...|...| | Ipomœa glaberrima | + |...|...| + |...|...|...| + | + |...|...| | Ipomœa pes capræ | + |...|...|...|...| + |...| + | + |...|...| |E Jacquemontia sandwicensis| + |...|...|...|...|...|...| + | ... | + |...| |E Lipochæta integrifolia | + |...|...|...|...|...|...| + | ... | + |...| | Morinda citrifolia |...| + |...| + |...|...|...| + | + |...| ? | | Mucuna gigantea | + |...|...| + |...|...| + |...| + |...|...| | Pandanus odoratissimus |...| + |...| + |...|...| + |...| + |...|...| | Portulaca oleracea |...| + |...|...|...|...|...| + | ... | + |...| | Scævola Kœnigii | + |...|...| + |...| + |...| + | + |...| + | | Sesuvium Portulacastrum | + |...|...|...|...|...|...| + | ... | + |...| | Tacca pinnatifida |...| + |...| + |...| + |...| + | + |...|...| | Tephrosia piscatoria | + |...|...| + |...|...|...| + | ... | + |...| | Terminalia Katappa |...|...| + | + |...|...| + |...| + |...|...| | Thespesia populnea |...| + |...| + |...|...|...| + | + |...|...| | Tribulus cistoides | + |...|...|...| + |...|...| + | ... | + |...| | Vigna lutea | + |...|...|...|...| + |...| + | + |...|...| | Vitex trifolia | + |...|...| + |...|...|...| + | + |...| + | +---------------------------+---+---+---+---+---+---+---+---+-----+---+---+ Footnote 5:

There are three endemic species here included which are preceded by E. Two species preceded by P are confined to Polynesia. Most of the plants are at present typically littoral, though often also occurring inland.

Footnote 6:

All fruits or seeds, an inch or over in size, that could not have been transported to Hawaii by birds are regarded as large.

NOTE 29 (page 54)

BOTANICAL NOTES ON THE COAST-PLANTS OF THE HAWAIIAN ISLANDS

[The following remarks have been extracted from my journals and represent some of the field-notes of journeys made in the more interesting localities.]

(1) _Walk along the Puna Coast, Hawaii, from Punaluu to Hilo_ (Dec. 26, 1896, to Jan. 6, 1897).—For the first two to three miles to Kamehame Point, the following plants were noticed on the flows of smooth ropy lava that formed the cliff-bound coast—Capparis sandwichiana, Jacquemontia sandwicensis, Ipomœa insularis, Lipochæta lavarum, Portulaca villosa, Tephrosia piscatoria, Tribulus cistoides, Waltheria americana, &c. Beyond this point Scævola Kœnigii was abundant in places on the old lava-flows near the sea, and further on patches of Myoporum sandwicense growing, not as a tree 20 to 30 feet high, as in the mountains, but as a prostrate shrub with fleshy leaves. Vegetation similar to that above described occurred on the surface of the old lava-flows that constituted the cliff-bound sea-border as far as Kapapala Bay. On the sandy beach at Kapapala Bay grew Ipomœa pes capræ, serving as host to Cuscuta sandwichiana. In the vicinity of the house at Keauhou there were a few Coco palms and Pandanus trees, whilst Capparis sandwichiana and Morinda citrifolia were growing on the adjacent lava-fields.

Morinda citrifolia and Tephrosia piscatoria grew on the lava flows between Keauhou and Apua. On the beach at Apua, Ipomœa pes capræ and Scævola Kœnigii were abundant, the last extending a few hundred yards inland on the lava. Further east the inland bush, made up of Cyathodes tameiameiæ, Metrosideros polymorpha, &c., descended to the coast to within a few hundred yards of the sea. In crossing the lava coast plains to Kapa-ahu I observed Morinda citrifolia growing frequently out of the cracks in the bare lava-rock, and an occasional solitary tree of Erythrina monosperma growing also from the fissures.

Before reaching Kapa-ahu we passed the site of an old coast village, named Laepuki, where there were growing from forty to fifty Coco-nut palms, as well as another village, represented by a solitary house, and named Kamomoa, where there were 27 Coco-nut palms and a few Pandanus trees. Kapa-ahu, with its numerous Coco-nut palms, was more like a South Sea coast village than any before seen; and the coast vegetation suddenly acquired a South Pacific character.

At Pulama, for instance, about a mile west of Kapa-ahu, where the ancient lava-flows, fairly vegetated, terminate at the sea in cliffs 20 or 25 feet high, there is a curious and quite unexpected development of a littoral flora such as we should see in the South Pacific. Here, growing on the broken lava surface at the brink of the cliffs and overlooking the sea, thrive Cæsalpinia Bonducella, Cocos nucifera, Ipomœa pes capræ, Ipomœa glaberrima, Morinda citrifolia, Pandanus odoratissimus, Scævola Kœnigii, Sesuvium Portulacastrum, Thespesia populnea, and Vigna lutea. This shore-belt of characteristic littoral plants is backed by vegetation more inland in its character, amongst which Aleurites moluccana, Dodonæa viscosa, Erythrina monosperma, Ipomœa insularis, I. bona nox, Osteomeles anthyllidifolia, &c., are to be observed. Such a shore-belt of typical littoral plants is rarely to be found in the large island of Hawaii; and its usual position at the margin of cliffs, and raised 20 or 25 feet above the sea, is rather suggestive of an uplift in recent times of this part of the coast.

Between Kapa-ahu and Kalapana is a low country occupied mostly by Guavas, and often turfy. At Kalapana, which is a large village situated on a grassy plain by the sea, Coco palms and Pandanus trees abound, and Mucuna gigantea and Cæsalpinia Bonducella are frequent near the coast, whilst Ipomœa pes capræ is common on the beach. Calophyllum inophyllum is planted near the houses. Here Osteomeles anthyllidifolia in its dwarfed form descends to the edge of the cliffs. About half a mile beyond Kalapana is the hamlet of Kaimu, and here among the Coco palms close to the beach I noticed four Loulu palms (Pritchardia Gaudichaudii). Beyond Kaimu the trees and shrubs of the inland wood, Metrosideros polymorpha, Cyathodes tameiameiæ, &c., descend on the spurs of old lava-flows close to the coast; whilst Pandanus and Morinda citrifolia with Mucuna gigantea are common near the sea as far as Kehena, where there are plenty of Coco palms. I approached Opihikao through as fine a Pandanus forest as I have ever seen, the large Bird’s Nest Fern (Asplenium nidus) growing half-way up their trunks, adding picturesqueness to the scene, whilst Mucuna gigantea was a common climber. Beyond Opihikao the inland woods descend to the coast. Thence on to Makuu the coasts are mostly occupied by Pandanus forests, and the lower coast road from Makuu to Hilo traverses a region where these Pandanus trees abound, extending far inland. Scævola Koenigii and Ipomœa pes capræ are common on the coast near Coco-nut Island, Hilo Bay.

It may be added that the agency of the wild goat explains the dispersal of Myoporum sandwicense, Morinda citrifolia, Tephrosia piscatoria, Waltheria americana, &c., over the almost bare surfaces of the lava flows on the Puna coast. Goat droppings were frequent under the patches of Myoporum and Waltheria. In some of them I found the entire seeds of Portulaca oleracea and the small cocci of Euphorbia pilulifera, weeds common in the district.

(2) _Coasts of the Kalae Promontory and its Vicinity, Hawaii._— This is the most southerly portion of the group, and it is on the eastern coasts of this district that many of the North American drift logs are embayed and stranded. At Kamilo, to the east of the promontory, there is a long beach of calcareous sand where Heliotropium anomalum, Scævola Kœnigii, and Tribulus cistoides grow in abundance, whilst Sesuvium Portulacastrum thrives on the beach and in brackish pools. Portulaca lutea (Sol.), Ipomœa glaberrima (Boj.), and Jacquemontia sandwicensis also occur. Where the beach-sand has encroached on the adjacent lava surface, the Scævola covers extensive tracts off the beach, and is stunted. I noticed a solitary thicket of Thespesia populnea on the beach.

The actual headland of Kalae is wind-swept and covered with grass, amongst which Portulaca villosa and Sida fallax thrive. By the sea occur Scævola Kœnigii and Ipomœa pes capræ, and there is some Sesbania tomentosa near the point. Waiheiaukini beach is shut in between the lofty arid slopes of the promontory on one side and a modern lava-flow on the other side. Here Scævola Kœnigii grows in quantity, together with Ipomœa pes capræ, Tribulus cistoides, Sida fallax, and Jacquemontia sandwicensis, whilst Cuscuta sandwichiana is abundant, finding its hosts in the first four plants just named.

(3) _South Kona Coast, Hawaii._—The coast here, as exemplified by that between Kapua and Hoopuloa, is mostly bare lava. Here and there, a little coral sand collects amongst the lava blocks of the rubbly shore, and it is in such places that Scævola Kœnigii and Ipomœa pes capræ find a home and apparently thrive, whilst Hibiscus tiliaceus and Morinda citrifolia grow behind. I observed Cordia subcordata and one or two specimens of Pritchardia Gaudichaudii by the coast on the south side of Milolii. Around a brackish pool at Kapua I observed Heliotropium curassavicum, and Acacia Farnesiana was to be seen growing on the beach at Okoe. On the lava coast between Hoopuloa and Papa, two miles to the north, Tephrosia piscatoria was very abundant.

(4) _North Kona Coast, Hawaii._—I examined the coast between Kailua and Kiholo. White beaches are common south of Keahole Point, the coast further north being usually lava-bound with sandy beaches here and there. Heliotropium anomalum, Ipomœa pes capræ, and Sesuvium Portulacastrum are the commonest beach plants on this coast. Scævola Kœnigii is also abundant in places, whilst Tribulus cistoides and Morinda citrifolia are also fairly common on the beaches. The Morinda also grows on the adjacent lava flats; but on both sand and rock it is evidently usually self-sown, since seedlings are to be seen near the older plants. Heliotropium curassavicum is to be seen here and there on the sand all along the coast, but nearly always associated with H. anomalum. Jacquemontia sandwicensis occurs occasionally on the beach; and Cuscuta sandwichiana is abundant in places, growing generally on Ipomœa pes capræ, but sometimes on Scævola Kœnigii. Brackish water ponds are common on the coast inside the beaches, Ruppia maritima flourishing in the water, with Sesuvium Portulacastrum growing at the edges. Sometimes Hala trees (Pandanus odoratissimus) fringe the borders of the pools. I noticed Pritchardia Gaudichaudii on the coast at Kiholo, and I learned that Cordia subcordata was once common here as on other parts of the Kona coast; but it has died out as in most other localities.

(5) _Kohala Coast, Hawaii._—Several littoral plants are scantily represented on the beach of black sand at the mouth of the Waimanu valley, especially Ipomœa pes capræ, Morinda citrifolia, Pandanus odoratissimus, and Scævola Kœnigii. The Pandanus covers the adjacent precipitous slopes up to a height of several hundred feet above the sea. Ipomœa pes capræ is abundant on the sand dunes backing the beach at Waipio. I observed Naias marina in the Waipio River just inside the mouth. No one seems to have recorded the plant from the group since Chamisso found it in Oahu.

(6) _Hamakua Coast, Hawaii._—Not many opportunities presented themselves on this cliff-bound coast of finding littoral plants. At the mouth of a gulch between Ookala and Laupahoehoe I found growing at the coast Vitex trifolia (var. unifoliolata) in quantity, together with Morinda citrifolia, Scævola Kœnigii, and Pandanus odoratissimus, the last-named clothing the hill-slopes overlooking the sea.

(7) _The Coasts of Oahu._—The littoral vegetation of the south-east portion of the island from Diamond Head round to Waimanalo is, as a rule, scanty. Ipomœa pes capræ and Tribulus cistoides prevail to Koko Head, and on the rubbly coast between that headland and Makapuu Point occur Tephrosia piscatoria, different species of Lipochæta, &c. Between Makapuu Point and Waimanalo, Scævola Kœnigii and Vitex trifolia (var. unifoliolata) are fairly abundant, the former growing on the rocky slope at the base of the cliffs, and raised perhaps some 20 feet above the sea. Along the whole east coast of the island the littoral vegetation is rarely well represented. However, Ipomœa pes capræ is common everywhere, whilst Scævola Kœnigii occurs frequently, and here and there a few plants of Morinda citrifolia are seen on the beach, while thickets of Hibiscus tiliaceus mark in some localities the mouths of streams.

On the north coast of Oahu, as on the Waialua and Waimea beaches, the one-leaved variety of Vitex trifolia is common, together with Ipomœa pes capræ and Euphorbia cordata; whilst Acacia Farnesiana is frequent on the Waialua beach, its pods being much appreciated by the cattle. Occasionally, as by the bridge at Waimea, Colubrina asiatica and Thespesia populnea are to be noticed.

Shore vegetation is a little better represented on the beaches at and near Kaena Point, the north-west corner of the island. Here on the sand we find often in abundance Heliotropium anomalum, the same variety of Vitex trifolia, Scævola Kœnigii, and Ipomœa pes capræ; whilst on the rocks bordering the beach occur Gossypium tomentosum, Jacquemontia sandwicensis, Tribulus cistoides, Vigna lutea, and more than one species of Lipochæta, the last being derivatives from the inland flora.

On the west coast of the island true shore-plants play an inconspicuous part. Ipomœa pes capræ is common on the beaches, and such plants as Acacia Farnesiana, Jacquemontia sandwicensis, Gossypium tomentosum, and Tribulus cistoides immediately border the beach. Ipomœa tuberculata is a frequent intruder as well as the recently introduced Algaroba tree (Prosopis dulcis). Acacia Farnesiana also extends inland, covering entire large areas and forming in the Waianae valley extensive thickets impenetrable for the cattle. It occupies great districts near the coast in different parts of Oahu, and with Hibiscus tiliaceus is to be found far inland. The cattle are active dispersers of its seeds. (See Note 30.)

True beach plants are infrequent at the mouth of Pearl Harbour, although the coast is well suited for them. Here I found Heliotropium anomalum, H. curassavicum, Jacquemontia sandwicensis, Lipochæta integrifolia (a true beach plant), Herpestis Monnieria, &c. Batis maritima occurs in one or two localities around Oahu, but it is, according to Hillebrand, of recent introduction.

NOTE 30 (page 58)

THE BEACH-DRIFT OF THE HAWAIIAN ISLANDS

It was pointed out by Dole long ago in one of the Hawaiian Club Papers (1868) that the existing currents bring to this archipelago only huge pine logs from Oregon, but no tropical fruits; and Hillebrand (p. xiv.) refers to the driftwood of pine logs from the north-west coast of America, stranded on the shores of these islands. This drift seems to collect in quantity in particular localities, as on the south-east coast of Hawaii between Honuapo and the Kalae promontory (especially on the Kamilo beach near Kaluwalu) and on the east coast of Oahu; and probably there are other favourable localities for catching the drift on the northern shores of Maui and Molokai.

It was on the south-east coast of Hawaii (on the beach at Kamilo and on the eastern side of the Kalae promontory) that this drift came particularly under my notice. Here the logs are stranded in abundance, in sufficient quantity, in fact, to build a town, and they were employed for building purposes by the manager of the neighbouring sugar-cane plantation. Several of the logs are of huge size, as much as 4 feet in diameter; and they are known locally as “white cedar” and “red cedar,” and characterised as Oregon timber. Some of them are extensively burrowed by the “teredo” and other boring mollusks. Others recently stranded are covered with barnacles (Lepadidæ), whilst others that have lain long on the beach are bare. I have seen these logs occasionally washed up at Punaluu and at different places on the lava-bound Puna coast. They apparently first strike the Puna coast, and are drifted along until they become embayed near the Kalae promontory, and ultimately stranded. Mingled with them on the beaches Pandanus trunks occur in number; they evidently hail from those parts of the Puna coast where Pandanus forests prevail, and thus they indicate the direction of the drift on the coast of this island. In places there was a considerable amount of small vegetable _débris_, sometimes partially concealed by the sand, and containing seeds and fruits in fair quantity.

The following seeds and fruits were collected:—

_Pandanus_ drupes, common; most of them fresh-looking, but a few much worn. _Thespesia populnea_, a few seeds. _Ipomœa pes capræ_, seeds, fair numbers. _Ipomœa bona nox_, seeds, a few. _Ipomœa glaberrima_, seeds, a few. _Argyreia tiliæfolia_, fruits and seeds, a few. _Strongylodon lucidum_, seeds, a few. _Cæsalpinia Bonducella_, a single seed. _Vigna lutea_, seeds, a few. _Calophyllum inophyllum_, a few fruits. _Ricinus communis_, a few, the seeds either free or in the cocci, and often empty or decaying. _Aleurites moluccana_, seeds, common, none sound, either empty or containing a rotten kernel: also a single fruit. One or two seeds not identified.

There was seemingly a total absence of the fruits or seeds of any littoral plant not found in these islands, such as I was familiar with in the South Pacific. In the mass this seed-drift could have been derived from the neighbouring coasts of the island. This is especially indicated in the cases of the fruits and seeds of Aleurites moluccana, Ricinus communis, and Argyreia tiliæfolia. The sound seeds of Aleurites do not float, the buoyant seeds being always empty, or nearly so; and the presence of the seeds in beach-drift, as explained on page 419, is due partly to the buoyancy of the empty seed and partly to the decay of the stranded fruit, the fruits being able to float for a week or two. So, also, the seeds of Ricinus, whether free or inclosed in the coccus, do not, when sound, float longer than a week or ten days. The capsules of the Argyreia can float two or three weeks, whilst the seeds vary in their behaviour, as observed on page 20. I noticed in places where the vegetable _débris_ was heaped up and exposed to the sun’s heat, that some of the Ipomœa seeds were germinating. It is to be remarked that horse-dung and goat-dung are always common in the beach-drift of these islands. Seeds are sometimes to be seen in the stranded material; and it was evident that the droppings of these animals can float for some weeks before breaking down.... I may add that large sponges, apparently of no value, are thrown up in quantities on the east side of the Kalae promontory.

Excepting the pine logs, the only things coming under my notice in this beach-drift that could be characterised without hesitation as non-Hawaiian, were two well-worn pieces of acid pumice, less than an inch in size. One of them was incrusted partially by the tubes of annelids, and both of them had evidently been drifting about in the Pacific for a long period, perhaps for years. They were such as occur in abundance on the beaches of the South Pacific, and, in fact, on all the shores of the Pacific Ocean, both temperate and tropical. Although I carefully searched the stranded drift of many beaches in this group, no other specimens of drift pumice were found.

On different parts of Oahu the beach-drift was always made up of materials derived from the vegetation of the coast adjacent. Of most frequent occurrence were the seeds of Ipomœa pes capræ and Vigna lutea, and the fruits of Scævola Kœnigii, Vitex trifolia, and Pandanus odoratissimus. In addition, the empty seeds of Aleurites moluccana were numerous, and there were occasional seeds of Thespesia populnea, Colubrina asiatica, and Mucuna gigantea. On one beach there were a number of fruits of Terminalia Katappa, showing but little signs of ocean travel, and evidently derived from trees in the vicinity. This tree was introduced by Europeans; but it is not unlikely that in a generation or two it will become, without man’s aid, one of the characteristic beach trees of Oahu. It may be remarked that the pods of Acacia Farnesiana, a shrub now growing abundantly in Oahu near the sea, are washed up in great quantities on the beaches of the west coast of this island, and the seeds are to be seen germinating in numbers on the beach, the seedlings striking into the sand. The pods float unharmed in sea-water for four or five weeks, but the seeds, when freed, sink.

Although the above evidence gives no indication of tropical drift of non-Hawaiian origin on the beaches, it is probable, for reasons adduced in Chapter VIII., that, in the winter, drift may be brought from tropical America.

NOTE 31 (page 59)

THE INLAND EXTENSION OF THE SHORE-PLANTS OF HAWAII

_Cæsalpinia Bonducella._—According to Hillebrand, this plant, so characteristic of the littoral floras of tropical regions, grows “in gulches of the lower plains on all the islands,” no reference being made to its occurrence on the beaches. It is very rarely to be seen on the beaches of the large island of Hawaii; but it is to be found on the lava-bound coasts, and from there it extends inland usually on old lava-flows for five or six miles, and reaches sometimes considerable elevations. In one locality I found it at 2,000 feet above the sea (see page 188).

_Cassytha filiformis._—Though a typical shore-plant in Fiji and other tropical localities, it is rarely so in these islands. Hillebrand says nothing of its station. It grows well in the lower open wooded regions, and is frequently found amongst the blocks of old lava-flows near the coast.

_Cuscuta sandwichiana._—Unlike its fellow parasite Cassytha filiformis, this species of Cuscuta, which is confined to this group, never came under my notice away from the beach; and Hillebrand speaks of finding it only at the coast (see page 366).

_Ipomœa pes capræ_, as I observed it in the islands of Hawaii and Oahu, is confined to the beach or to neighbouring sand-dunes. Hillebrand makes no reference to its occurrence inland. This species in these islands offers thus a great contrast to its behaviour in Fiji.

_Scævola Kœnigii._—Whilst most at home on the sandy beaches, this plant is also frequently met with in the island of Hawaii on scantily vegetated lava-flows near the coast; but I never noticed it more than a few hundred yards from the sea.

_Tephrosia piscatoria._—Though it may occur on the beach, it is generally found as described by Hillebrand on the rocky or rubbly ground at the back of the beach, as well as further inland. It is common on the old lava-fields of the island of Hawaii near the coast; and, according to the natives, its seeds are disseminated by the wild goats that frequent these localities.

_Tribulus cistoides._—Hillebrand observes that this plant is found along the sea-shore and on the lower plains. I found it most frequently on the beaches and on the old lava-flows near the sea.

_Vitex trifolia, var. unifoliolata._—It is confined, as Hillebrand remarks, to the beaches. Neither in Oahu nor in Hawaii did I ever find it straying inland, which is the more remarkable since this variety, or one closely similar to it, is one of the most characteristic inland plants of the Fijian strand-flora.

_Vigna lutea._—This plant was found by me growing on the beaches and in their vicinity. Hillebrand merely speaks of it as “growing at short distances from the shore.”

Some of the trees, usually littoral in their station in the tropical Pacific, which are regarded as having been introduced in early times into the Hawaiian group by the Aborigines (see Chapter VII.), behave, nevertheless, quite like indigenous plants in the inland regions and in the lower levels. This is true, for instance, of Hibiscus tiliaceus and Pandanus odoratissimus, the last-named forming forests at the sea-board extending in places far up the mountain slopes. The same, however, may be said of other plants known to have been introduced since the discovery of the islands, as in the cases of Cactus Tuna and of Ricinus communis; and it also applies to Aleurites moluccana, the Candle-nut Tree, which, although it could only have been introduced by the Aborigines, now forms forests on the lower slopes of the mountains.

NOTE 32 (pages 19, 112, 165)

THE FIJIAN SPECIES OF PREMNA

I was much interested in the small trees and shrubs of this genus in Fiji, more especially on account of the relation between the shore and inland species. This is an Old World genus containing some eighty species mainly characteristic of tropical Asia and Malaya, and represented in the South Pacific archipelagoes by two species, one Premna taitensis or tahitensis, spread over the region and very near P. integrifolia, an Asiatic species; the other Premna serratifolia, an Asiatic plant found in Fiji, the Marquesas, and other groups. Without endeavouring to give a precise value to the Fijian plants, I will merely describe the prevailing forms, which are, however, connected by intermediate varieties. These trees, I may add, are known by the same name in the various Pacific groups, “Avaro” or “Avalo” in Tahiti, “Alo-alo” in Samoa, “Yaro” and “Yaro-yaro” in Fiji.

The Fijian plants may be thus described.... (_a_) Premna serratifolia, an inland tree, growing in open woods and on the outskirts of the forest, 25 to 30 feet high, more or less hairy, leaves coarsely serrated with long tapering points, putamen prominently tuberculated and thick-walled.

(_b_) Premna taitensis or P. integrifolia, a low straggling coast tree or shrub of the beaches, the coral islets, the swampy borders of the estuaries, and the inland talasinga plains, its usual height being eight to ten feet, except in the inland plains, where it is dwarfed, and three to five feet high. It is more or less glabrous, the leaves being typically entire with obtuse or retuse and mucronate apices. The putamen is thin-walled and relatively smooth. (_c_) Intermediate forms found generally in the inland plains or talasinga regions.

_On the Modes of Dispersal._—Speaking generally, the small drupes of both species float at first, but the soft parts are soon removed by decay, and the stone is freed. In the case of the coast species, P. taitensis, the stones float indefinitely and are often found afloat in rivers. In the case of the inland tree, P. serratifolia, most of the stones sink at once, whilst the others sink in a few days. It is probable that currents are one of the effective agencies in distributing the coast species, but this could not apply to the inland tree. The fruits of both the inland and the coast species would attract birds, and the stones would resist injury in their crops. This is the agency advocated by Prof. Schimper for the shore species, P. integrifolia, of Indo-Malaya; and fruits referred with a query to this genus were found in the collection of seeds and fruits obtained by me from the crops of pigeons in the Solomon Islands (_Bot. Chall. Exped._, Introd. p. 46,