CHAPTER XXV

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS (_continued_)

THE AGE OF THE MALAYAN PLANTS AS REPRESENTED IN THE LOW-LEVEL FLORA OF HAWAII AND IN THE BULK OF THE FLORAS OF THE FIJIAN AND TAHITIAN REGIONS

_The Age of Wide Dispersal over the Tropical Pacific._

The widely dispersed genera which possess only peculiar species in Hawaii.—Pittosporum.—Reynoldsia.—Gardenia.—Psychotria.—Cyrtandra—Freycinetia.—Sapindus.—Phyllanthus.—Pritchardia.—Summary.

WE pass now from the consideration of the mountain-flora of Hawaii and its scanty representation in the Fijian and Tahitian regions to a discussion of the low-level Hawaiian flora, belonging to stations under 4,000 or 5,000 feet, and of the corresponding floras of the other two regions. It has been previously pointed out that in mass the plants of Fiji and Tahiti correspond to the low-level flora of Hawaii.

There are numerous ways of comparing this era of the non-endemic genera of these three regions of the Pacific. The necessities of space, however, compel me to treat the subject only in an illustrative fashion, and in adopting the plan which seems easiest and simplest I have also been obliged to keep my limitations mainly in view.

THE WIDELY-DISPERSED GENERA WHICH POSSESS ONLY PECULIAR SPECIES IN HAWAII.

Amongst the oldest denizens of the Pacific islands in this era of the non-endemic genera may be taken those genera of flowering plants which are found in all three regions, Hawaii, Fiji, and Tahiti, but possess in the first group only endemic species, whilst in the other two regions they may include species both confined to and occurring outside the respective groups. They represent an age of wide dispersal over the Pacific, an age which for Hawaii has long since passed away, since all the genera have been disconnected from the outer world, whilst in the groups of the South Pacific they as a rule in each case remain in touch through some of the species with the groups around.

The problem of plant-distribution in the Pacific thus assumes a different aspect in an age which we term Malayan or Indo-Malayan, since the bulk of the plants are thence derived. The earliest age of the Coniferæ was, as we have seen in the previous chapter, restricted to the region of the Western Pacific. The following age of the Compositæ and the Lobeliaceæ was concerned with the regions of Tahiti and Hawaii. Now, however, in the Malayan era, the whole of the tropical Pacific is concerned. Yet, although we shall still regard, for purposes of convenience, the groups of Fiji, Tahiti, and Hawaii as the three foci of plant-distribution, it will soon become apparent that in future there will be in reality only two regions to deal with, the Hawaiian in the North Pacific, and the whole region of the South Pacific extending from Fiji to Tahiti and as far east as the islands stretch. It will be also seen that in making our comparison we shall sometimes have to regard each of the principal Hawaiian islands as the equivalent as a plant-centre of an entire archipelago of the South Pacific.

The genera that are here selected to represent this epoch of wide dispersion are very characteristic of the floras of the Pacific islands. Genera like Pittosporum, Gardenia, Psychotria, Cyrtandra, Freycinetia, and others one meets with everywhere in the larger islands, and it should be observed that they are predominantly Old World, and more especially Malayan, in their origin, not a single purely American genus, unless we except the decadent genus of fan-palms, Pritchardia, occurring among them. Here we notice [what we shall see is especially typical of the era of the non-endemic genera, excepting those of the lofty uplands of Hawaii] that the frugivorous bird has been the principal agent in dispersing the plants, quite two-thirds of the total genera possessing drupes or berries that would attract such birds. The transport of seeds or seedvessels in birds’ plumage, which was a conspicuous feature in the case of the mountain-flora of Hawaii, is not a feature of this age of wide dispersal of tropical plants over the Pacific.

The genera selected to represent this age are given in the following table. Those on which my observations directly bear, or in which I was particularly interested when in the Pacific, will be discussed in detail from the standpoint of dispersal; whilst only a brief reference will be made to a few of the others, not, however, from lack of materials at my disposal, but merely to keep this volume within moderate bounds.

_Genera selected to represent the Age of Wide-dispersal of Indo-Malayan or Malayan Plants over the Pacific, and possessing in Hawaii only Endemic Species._—Most of the genera of this age are exclusively from the tropics of the Old World, whilst those found on both sides of the Pacific can be shown in most cases to have been derived from the same source, and only very few, like Pritchardia, can be traced to America.

Pittosporum (Pittosporeæ). Sapindus (Sapindaceæ). Reynoldsia or Trevesia (Araliaceæ) Gardenia (Rubiaceæ). Psychotria (Rubiaceæ). Cyrtandra (Gesneraceæ). Phyllanthus (Euphorbiaceæ). Pritchardia (Palmaceæ). Freycinetia (Pandanaceæ).

PITTOSPORUM (Pittosporeæ).

This genus, which contains nearly a hundred species, usually of small trees, is widely spread in the warmer regions of Africa, Asia, Australia, and New Zealand. It is also especially a genus of oceanic islands, occurring not only in those of the Pacific but also in Madeira and Teneriffe in the Atlantic.

Though found in most of the larger Pacific groups, it has apparently never been recorded from Samoa. From Hawaii ten species are known, all peculiar to that group. About half a dozen have been described from Fiji, of which three at least have been observed outside the group in the neighbouring Tongan Islands. Rarotonga possesses a peculiar species which, however, is so near to two other Fijian and Tongan species that, according to Cheeseman’s memoir, they may have to be subsequently united. Tahiti is credited by Drake del Castillo with a solitary species widely distributed in the Old World, whilst in the _Index Kewensis_ a peculiar species is assigned to it. They form small trees of the wooded mountain-slopes of Fiji; whilst in Hawaii, beside occurring in the lower forests, they may extend to altitudes of between 5,000 and 7,000 feet. In the connection that more or less exists between the species of the South Pacific archipelagoes, and in the endemic character of all the Hawaiian species, we see the principle exemplified that there are two regions of distribution in the islands of the tropical Pacific—the Hawaiian region and the South Pacific region.

Before their dehiscence, the wrinkled, woody capsules would seem very unlikely to attract birds; but the observer on handling an opening fruit, with its orange or brightly coloured lining and displaying black or dark-purple seeds immersed in a semi-liquid pulp, would form a different idea of the plant’s capacity for this mode of dispersal. The mature dehiscing fruits are very conspicuous on the tree; and the seeds covered with the “sticky” material of the pulp might possibly adhere to birds pecking at the fruit. But this would only aid in local dispersion, since the weight and size of the seeds, 5 to 8 millimetres (2/10 to 3/10 inch), would unfit them for this mode of transport across an ocean. They are, however, sufficiently protected by their hard tests to be able to pass unharmed through a bird’s intestinal canal.

Yet the distribution of the species of Pittosporum in the Pacific would show that their dispersal is more a matter of the past than of the present. Out of the ten peculiar Hawaiian species, Hillebrand designates none as generally distributed over the group. But it is evident that, though it is on the point of breaking off, some sort of connection still exists in the South Pacific between the Tongan and Fijian species, and until recently between the species of those two groups and of Rarotonga.

REYNOLDSIA (Araliaceæ).

The Polynesian genus of Reynoldsia, originally established by Gray, is merged by Hooker and Bentham into the Malayan genus Trevesia, a step that brings the Pacific plants into line with many other of the plants hailing originally from the Old World. The significant fact in the distribution of this genus of small trees in the Pacific is that its dispersal over the ocean has ceased long ago, since the three species here occurring are restricted each to a particular group, namely, to Hawaii, Tahiti, and Samoa. Yet the inter-island dispersal still continues in the Hawaiian Group, the species characteristic of that archipelago being found in all the islands.

Reynoldsia sandwicensis came frequently under my notice in Hawaii, and the fairly fleshy drupes, about one-third of an inch, or 8 millimetres, in size, with their crustaceous pyrenes appeared to me well fitted for assisting the dispersal of the plant by frugivorous birds. Yet here the same question arises that presents itself with so many other Hawaiian plants, and that is, How has it happened that the birds have continued to disperse the species over the scattered islands of this group long after they ceased to transport fresh seeds from the outside world? The answer is an obvious one. The birds that originally brought the seeds of the parent species from some distant region came at last to remain permanently in the Hawaiian Group, and not only the plant but probably also the bird has since undergone specific differentiation. This link between bird and plant in the floral history of a group of Pacific islands is the common theme of the story of most of the endemic species of plants in this region of the globe.

GARDENIA (Rubiaceæ).

This genus, comprising about a hundred known species, is spread over tropical Africa, Asia, and America, and over all the groups of the tropical Pacific. On account of their handsome, white, scented flowers these shrubs are much appreciated by the Pacific islanders, who employ the flowers for personal decoration. Some ten species have been described from the groups of the open Pacific, all of which, with the exception of Gardenia tahitensis, which ranges the South Pacific from Fiji to the Marquesas and Tahiti, are seemingly peculiar to the different archipelagoes. Thus there are some six species endemic to Fiji, one to Samoa, and two to Hawaii.

The Hawaiian Islands are, however, quite isolated in this respect, since the group possesses only peculiar species; whilst a solitary species keeps up the connection between the groups on the south side of the equator. The Gardenias thus tell the same story of complete isolation in Hawaii, and of partial isolation in the archipelagoes of the South Pacific that is repeated by many other Pacific genera. Yet in Hawaii there has subsequently been some inter-island dispersal, since the species are not restricted each to a single island, but are found on two or three islands. The significance of the relation of the Hawaiian Gardenias to those of the combined Fijian and Tahitian areas consists in regarding the two regions, the Hawaiian and the South Pacific, as of equivalent value, and each large Hawaiian island as equivalent to one of the southern archipelagoes.

_The Station of the Pacific Gardenias._—Although they may occur in the forests, the Gardenias of the Pacific are most characteristic of dry, thinly vegetated localities, and they have an inclination for the vicinity of the coast. In the Tahitian Group, as we learn from the writings of Nadeaud and Drake del Castillo, Gardenia tahitensis thrives much better on coral islands than on volcanic soils, and, in fact, rarely quits the “_région madréporique_.” It is sometimes planted in Polynesia near the houses, and both Nadeaud in Tahiti and Cheeseman in Rarotonga consider that it was probably introduced into those islands before the arrival of Europeans. The aborigines may have assisted in the dispersal of the genus to a small extent, but from the presence of peculiar species in Hawaii, Samoa, and Fiji it is apparent that the genus is truly indigenous in the Pacific islands, and long antedated their occupation by man. This is also evident from the station of the species in Hawaii, Samoa, and Fiji. In Hawaii they may be found on the dry forehills in the vicinity of the sea-border. In Samoa, as Reinecke informs us, Gardenia tahitensis is very widely spread in the mountain-forests, whilst the endemic species is found thriving in inundated coast districts. In Fiji I found the Gardenias to be especially characteristic (as is also pointed out by Horne) of the dry districts on the leeward side of the larger islands. On the rolling “talasinga” or “sun-burnt” plains of the north side of Vanua Levu they thrive in numbers; and here their leaf-buds and the extremities of the young shoots are often tipped or covered over with an amber-like gum-resin which the natives chew.

_The Mode of Dispersal of the Pacific Gardenias._—The fruits of this genus are usually described as indehiscent. If this were true of Pacific plants it would be very difficult to explain the dispersal of hard, dry fruits an inch in size over this region. In the case of two or three Fijian species, I paid especial attention to this point by examining the plants in fruit. As exhibited in Fiji the fruits are globose, hard, and almost stony, with persistent adherent calyx, the seeds lying horizontally in a pulp at first firm and subsequently softening as the fruit matures. The fruits are not as a rule to be observed opening on the plant; but they are to be seen dehiscing septicidally on the ground beneath, the detached woody valves being scattered around. If one of the fruits gathered from the plant is kept soaking in water for some time it will begin to dehisce; and this is probably what occurs with fallen fruits in wet weather. Dr. Hillebrand regards the fruits of the Hawaiian species as indehiscent. I did not myself examine them, but it is not improbable that, like those in Fiji, they dehisce whilst lying soaking on the ground.

Judged merely from the dispersal standpoint, the fruits of the Fijian Gardenias come near to those of Pittosporum, and both can be in a sense described as baccate capsules. The flat, crustaceous seeds of Gardenia, which are usually two or three millimetres in size, are also well fitted for passing without injury through the digestive canal of a bird. It is likely that the two genera have been dispersed in the Pacific by the same kind of birds; and it should be remarked that their distribution is somewhat similar, both belonging to the warm regions of the Old World.

It might at first appear from some experiments of mine made in Fiji that the dried fruits of Gardenia could be dispersed over oceans by the currents. This receives some support by the preference for a littoral station sometimes shown by G. tahitensis in Tahiti, and by the occurrence of G. zanguebarica in the East African strand-flora (Schimper’s _Ind. Mal. Strand-flora_, p. 131). It will, however, be pointed out that currents could only have aided the dispersal of the genus to a limited extent. The fresh fruits of Fijian species, with or without the adherent calyx, have little or no buoyancy, and the seeds sink even after drying for months. But it was ascertained that fruits which had been kept for three months floated after four or five weeks’ immersion in sea-water. On examination, however, it was found that the valves gaped a little, being only held in apposition by the adherent calyx, and that water had penetrated into the interior, the pulp being in a state of decay. The fruits were, in fact, kept afloat in the latter part of the experiment partly by the investing calyx and partly by gas generated in the decomposing pulp. Ultimately they broke down altogether and the seeds sank. In the “rough-and-tumble” of ocean-transport this could scarcely be deemed an effective means of dispersal; and in the open sea a fortnight would probably represent the limit of the floating power. It is to the agency that has distributed the genus Pittosporum over the Pacific that we must look for the explanation of the dispersal of Gardenia over the same ocean, namely, to birds.

PSYCHOTRIA (Rubiaceæ).

We find in this large genus of the Old and New Worlds a typical example of the plants with fleshy drupes containing hard pyrenes that represent, from the standpoint of dispersal, a common Rubiaceous type of plant in the tropical Pacific. Such plants, of which those of Coprosma and Nertera may be cited as other instances, are in a generic sense always widely distributed in these islands. They are eminently suited for dispersal by frugivorous birds; and it is a matter for surprise, therefore, that in a genus like Nertera the solitary Pacific species has such a wide range, whilst with Psychotria and Coprosma the numerous species are usually restricted to particular groups. Genera doubtless have their periods of development and decadence in the Pacific, and probably Nertera is to be regarded as a decadent genus. These Rubiaceous genera, however, appear to be well fitted for the investigation of the centres of dispersal of particular genera and of their relative age.

The Psychotrias in these islands are typically shrubs of the shady woods, and they may be seen thriving best where the forest-growth is rank and the humidity greatest. Their bright red ovoid drupes, which range from eight to twenty-five millimetres in length (1/3 to 1 inch), would readily attract birds, and their crustaceous pyrenes, that vary between five and eight millimetres (1/5 to 1/3 inch) in length, would pass unharmed through a bird’s digestive canal. That fruit pigeons can distribute their seeds over the Pacific has been long established, and Mr. Hemsley includes Psychotria amongst those genera which, from the collections of fruits and seeds found in the crops of fruit-pigeons, made by Professor Moseley, myself, and others, in the groups of the Western Pacific, are “known to be dispersed by birds in Polynesia” (_Introd. Bot. Chall. Exped._, p. 45). It is thus hardly necessary to point out that neither the entire fruits nor the separate pyrenes could be transported by the currents, my observations showing that in both cases they sink at once or in a day or two.

Psychotria, however, is an enormous genus including, according to the _Index Kewensis_, some 600 or 700 described species, distributed in the tropics all over the world, and also extending into subtropical regions, the greatest concentration being in America. It is described in the _Genera Plantarum_ as a polymorphous genus distinguished by no certain characters from some other genera of the tribe of the Rubiaceæ to which it has given its name. We have here a genus that has overrun the tropical regions of the world, probably originating in America; and we may contrast it with the relatively small Rubiaceous genus of Coprosma (with its three score of species, and quite comparable with it from the standpoint of capacity for dispersal), that, having its birthplace in New Zealand, is only beginning to reach the mainlands of the New and the Old World.

One is a genus of the tropics and the other is a genus of south temperate latitudes; and both have occupied the Pacific islands; but Coprosma naturally finds its most appropriate station on the cool uplands of Hawaii and Tahiti. We may ask, indeed, whether the great contrast in the fecundity of the two genera, dispersed as they are in the same fashion by the agency of frugivorous birds, is to be connected with questions of relative antiquity or with geographical position. It would certainly have been a more difficult task in the past, other things being similar, for a New Zealand genus to stock the temperate regions with its species than for a tropical American genus to overrun the warmer regions of the globe. However that may be, the age of dispersal of both genera is largely over now.

A vast genus like Psychotria, that is not sharply defined from other genera, presents difficulties to the systematic botanist which are reflected in a complex synonymy; but there are certain broad facts which the student of dispersal can gather for himself without much difficulty. When we look at its distribution in the islands of the open Pacific, we find that the genus attains its greatest development in the Western Pacific, there being from thirty to forty species known from Fiji and quite a dozen from Samoa, and that it shades away as we proceed eastward and northward, some six species being recorded from Tahiti and the Marquesas, two from Hawaii, and one from Juan Fernandez near the South American mainland. The arrangement of the species shows fairly conclusively that the genus Psychotria, as it is found in the Pacific, has, like most of the other plants of this era of non-endemic genera, been derived from the Asiatic side of the ocean. (The absence of species of this genus from Mr. Cheeseman’s Rarotongan collections seems strange. It is represented by some species in Tonga, and it is extremely probable that it will be subsequently found also in the Rarotongan group.)

That the age of dispersal of the genus Psychotria over the Pacific islands has almost passed away is evident from the circumstance that of the half-hundred species known from these groups, all but some four or five are confined to particular groups. There is one species, P. insularum, that ranges over the South Pacific from Fiji to the Tahitian region; and there are two or three others that keep up a connection between the adjacent groups of Fiji, Samoa, and Tonga, the last having no peculiar species; but, apart from these indications, isolating influences generally prevail. The two Hawaiian species are both endemic and are only recorded from the island of Kauai, so that in that archipelago there has not even been inter-island dispersal of the genus. For Fiji it would seem from the _Index Kewensis_ and other authorities that at least two-thirds of the species are confined to the group. Of the dozen Samoan species only two or three are known outside the islands. Four out of the five Tahitian species are peculiar, and the only Marquesan species named by Drake del Castello is endemic. Even the solitary species of Juan Fernandez is endemic, there attaining the dimensions of a fair-sized tree. It forms the subject of an illustration in Schimper’s _Plant-Geography_, page 491.

Speaking generally, birds may be said to have almost ceased dispersing this genus over the Pacific. This is not because birds have ceased to be partial to the fruits, but because the frugivorous birds that used to range over the Pacific archipelagoes now restrict their wanderings to the limits of a single group. If we find occasionally in other parts of the world, as in the occurrence of a Florida species of Psychotria in the Bermudas, some evidence of a dispersal still in operation, this is nothing more than we observe in the case of a few of the Polynesian species now. The connection between birds and plants in the Pacific is discussed in Chapter XXXIII. In this ocean the dispersal of the genus is now practically dead, and Psychotria presents no exception to that general tendency towards isolation and differentiation exhibited by most genera of the tropical Pacific as the result of failure of the means of dispersal.

CYRTANDRA (Gesneraceæ).

This remarkable genus of shrubs, which forms the subject of an important memoir by Mr. C. B. Clarke (_De Cand. Mon. Phan._ v. 1883-87), offers, as Mr. Hemsley remarks, an example of a Malayan genus extending to Polynesia and there developing numerous species. Of some 180 known species, about 80 or nearly half are confined to Polynesia, the rest being mainly Malayan. Of the Polynesian species about thirty are Hawaiian, twenty Fijian, fifteen Samoan, and twelve Tahitian; whilst solitary species are restricted to Tonga and Rarotonga respectively.

The most significant feature in the distribution of this genus in Polynesia is not only, as is pointed out by Mr. Clarke, that every group has its peculiar species, but that very few species are found in more than one group, and that even in the same archipelago each island has its own species. Thus, of the thirty Hawaiian species, all of which are peculiar to the group, only two or three, according to Hillebrand, are at all generally distributed over the islands, whilst four-fifths have not yet been found to be common to more than one island. So again, all the species found in the Tahitian Group proper are peculiar, with the exception of one extending to the neighbouring Paumotu Islands; and even Rarotonga has its own species. In the region comprising Fiji, Tonga, and Samoa the same rule prevails, only two or three species connecting the three groups together. There thus seems to be not only a complete suspension of the dispersal agencies between the various archipelagoes, but also often between the several islands of a group. This is particularly to be remarked with the relatively contiguous groups of Fiji, Samoa, and Tonga, since with most other genera a number of species are common to all three archipelagoes. “The polymorphism of the Hawaiian Cyrtandras,” says Hillebrand, “is extraordinary: no single form extends over the whole group, and not many are common to more than one island. The variations affect nearly every part of the plant, and branch out and intercross each other to such an extent that it is next to impossible to define exact limits of species.” Genera, however, run riot in other groups of the Pacific besides Hawaii, and Reinecke uses much the same language with reference to Elatostema, an Urticaceous genus in Samoa, attributing the wealth of forms to the sensitiveness of the plants to the varying conditions of station (see Chapter XXVII).

The behaviour of Cyrtandra in the Pacific is rather startling to the student of plant-dispersal when he reflects on the suitability of the berries for dispersing the plant through the agency of birds. That the vegetation of oceanic islands should be of an endemic character is a fact, remarks Mr. Clarke, that is illustrated by many other orders besides the Gesneraceæ. But the point we have to remember is that not only does the genus Cyrtandra display the same prolific character in the large continental islands of Malaya, such as Java, Sumatra, and Borneo, each of which possesses at least a couple of dozen species, but that this seems to be a feature of the tribe Cyrtandreæ and of the whole order. The genera, as observed by Mr. Clarke, are very continuous in their areas of distribution, and in the tribe Cyrtandreæ there are very few species that extend to more than one region, whether on the mainland or in an oceanic archipelago. In the Himalayas, he says, closely allied species of Didymocarpus are confined to single districts, although there appears no reason either in soil or climate why they should not spread to the adjacent valleys.

There is therefore, we may infer, nothing peculiarly characteristic of insular floras in this prolific display of the genus Cyrtandra in the Pacific, except that it is rather more pronounced in an oceanic group than in a continent. The same general cause is working alike in an island in mid-ocean, in a large continental island bordering the mainland, and on the mainland itself. With the Pacific Cyrtandras as with the British species of Rubus the variability may be so great that the ordinary agencies of dispersal fail to keep it in check; and when, as in the Pacific islands, the suspension of the activity of these agencies is complete, the formative energy of the species knows no bounds other than the determining limits of station. Our lesson from the Pacific Cyrtandras is therefore this. The isolation of the oceanic archipelagoes may not explain the endemic character of the flora, but only the extreme degree to which the endemism is carried. When a genus is in its prime, it can defy all the limiting conditions imposed by similarity of station and by free and unchecked means of dispersal, the essential marks of a species or a genus having probably in their development little or no connection with environment.

The Cyrtandras of the Pacific Islands are most frequent where vegetation is rank, as in moist woods, in humid valleys, and in shady ravines and gorges; but they may also occur in more exposed and drier stations. They often grow gregariously, and Schimper says the same of them in the Java forests (_Plant-Geography_, pp. 291, 297).

The fruit of the genus is described by Clarke as a fleshy or a coriaceous berry. Almost everywhere in the Pacific groups the berry is white and fleshy; but it is noteworthy that out of the nine Tahitian species where the fruit is particularised by Drake del Castello, in two cases it is designated a capsule and in seven a berry. It is in this connection worth remarking that in Malaya other genera of the tribe often have capsular or dry and coriaceous berries. The conspicuous white berries of the Pacific species would readily attract birds, and their minute roughened seeds scattered through the pulp might readily adhere to their plumage or even be ejected unharmed in their droppings. As respecting the capacity for dispersal, the Pacific Cyrtandras come near the Hawaiian endemic genera of Lobeliaceæ with baccate fruits and minute seeds. Speaking of Malayan genera of the tribe Cyrtandreæ, Mr. Ridley says that their dry, dull-coloured, and inconspicuous corky fruits are often devoured by animals. The seeds, on account of their roughened surface, adhere to rocks and other surfaces and readily germinate.

FREYCINETIA (Pandanaceæ).

If there is any genus of tropical plants to which the student of distribution can look for guidance in the region of the Pacific, it is to Freycinetia as dealt with by Dr. Warburg in his monograph on the order (Engler’s _Pflanzenreich_, iv. 9, 1900). Its characters and its distribution are well defined; and here, if anywhere, we might be able to work out the history of a genus. In the words of the German botanist, it stands quite apart from Pandanus and Sararanga, the two other genera of the order. When Hillebrand was preparing his work on the Hawaiian flora, more than a quarter of a century ago, only about thirty species were known. Warburg’s list, excluding doubtful forms, comprises sixty species, and even this number the author surmises will be doubled in future years. The later investigators, however, have not materially extended the range of the genus; and the statement of the botanists of a generation ago, that it extends from Ceylon through Malaya and Australia to New Zealand, and is found on almost every elevated island of the Pacific, can only be supplemented by extending its area to the Asiatic mainland in Burma where a wide-ranging Malayan species exists.

It is, however, remarkable that no endemic species can be with certainty accredited to the mainland of Asia either in Burma or in the Malay peninsula where the genus also occurs. The Malayan region from Java to the Philippines possesses quite three-fifths of the species, and it is singular how few wide-ranging species there are. The Philippine Islands, Borneo, Celebes, Sumatra, Java, New Guinea, &c., have all their own species, the only wide-ranging plant being Freycinetia angustifolia, which occupies the region from Burma to Java and Borneo. So also in the Pacific, there is no widely distributed species, every group possessing its own plant or plants, and there does not appear to be any Freycinetia that is common to two groups. Thus, Hawaii and Tahiti each have their own species. Rarotonga, according to Cheeseman, owns a peculiar but not yet fully described form. Samoa has two and Tonga has one species. Westward from Tonga and Samoa the numbers of species increase, Fiji possessing five and New Caledonia four. Australia and New Zealand each claim two species as their own.

Dr. Warburg, who has studied the genus in its home, remarks on page 43 that none of the species possess any means of dispersal enabling them to cross an ocean; and he connects with this the fact that the genus is only found (to use his own words) on islands like those of Samoa, Tahiti, and Hawaii, that possess a “palæobiotic” nucleus (_paläobiotischen Kern_) and not on islands like the Bonin Islands of new formation (_auf Neubildungen_). This attitude towards the problem of plant-distribution in the Pacific is backed by a great experience; but it is one, of course, that is directly opposed to the line of argument followed in these pages; and it is needless to say that it is not encouraging to the student of plant-dispersal. Yet one could hardly look upon the islands of the Tongan Group with their representative of the endemic Freycinetias as of more ancient origin than the Bonin Islands that have none; and plants that find their homes on the peaks and in the forests of mountainous islands would rarely find a suitable station on the low coral islands of the Pacific. It is, however, noteworthy that Professor Schimper is inclined to include a species of Freycinetia as amongst the strand-flora of the coral islands of the Java Sea (_Ind. Mal. Strand-flora_, p. 134). With regard to the question of the means of dispersal of Freycinetias, it will at once be shown that these plants possess many opportunities for dispersal by birds.

Though in our own time dispersal by birds between the various Pacific archipelagoes is often largely suspended, the inter-island dispersal in each group is usually active through the agency of birds, now like the plants they distribute confined to each group. Thus with Freycinetia we find that, notwithstanding that each Pacific group is, as regards this genus, isolated from the others, the separate islands, as in the case of those of Hawaii, may possess a common species dispersed over the area. The ripe fruit, which consists of a number of berries in a head or spike, is juicy and pulpy, and contains in each berry a large number of minute oblong or fusiform seeds, usually one or two millimetres long and possessing thick toughish tests. Birds, indeed, are fond of pecking at the ripe fruit-heads in Hawaii. Thus we learn from the _Aves Hawaiienses_ of Wilson and Evans that a Grosbeak (Psittacirostra) and the Hawaiian Crow (Corvus tropicus) feed principally on ripe Freycinetia fruits, the seeds having been often found by Mr. Wilson in the stomach of the former bird. No doubt these birds distribute the seeds over the islands of the group. Mr. Perkins tells me that the Grosbeak is found unmodified all over the group, and that it no doubt frequently gets carried _nolens volens_ from one island to another. In his memoir on the birds in the _Fauna Hawaiiensis_, he remarks that the essential food of the “Ou,” the native name of this bird, is the fruiting inflorescence of Freycinetias. The “Oo” (Acrulocercus) and the Hawaiian Crow above mentioned, as he also observes, feed on these ripe red fruits. Like Mr. Wilson, he sometimes found the Crow absolutely filled with this food to the exclusion of all others (see Chapter XXXIII). Facts of a similar kind came under my notice whilst in these islands. Thus on one occasion I observed, on a leaf below a fruit-head that had been partly eaten by a bird, a pellet half an inch long composed entirely of Freycinetia seeds well soaked with the gastric juices and apparently only recently disgorged. Sir W. Buller refers to different New Zealand birds, as the Banded Rail (Rallus philippensis), the Kaka Parrot (Nestor meridionalis), and the “Tui” (Prosthemadera), that live on the “sugary flowering spadices” of Freycinetia Banksii. One can legitimately suppose that they also attack the juicy berries. It is singular that as we learn from Dr. Warburg (p. 17), Flying-Foxes (Pteropidæ) feed on the flowers and top-leaves of many species of Freycinetia, and he considers that they would aid in fertilisation by carrying about the pollen in the hair of the head. Here again it would seem to us highly probable that whilst brushing past a ripe fruit-head these bats might readily carry away in their fur some of the minute seeds, which in the fresh berry are “sticky” or adhesive.

Just as it was possible in the case of Coprosma in the South Pacific (see page 296) to connect its distribution with the range of the Purple Water-Hens (Porphyrio), so it may perhaps be legitimate to associate the range of Freycinetia over Polynesia with the distribution of the Honey-Eaters (Meliphagidæ) in the Pacific, a family sometimes possessing peculiar genera as in New Zealand and Hawaii, and one in which the species have usually a very confined range, being sometimes limited to a single island (Newton in _Encycl. Brit._ xii. 139). To this family belongs the New Zealand “Tui” above mentioned; and it may be remarked that these birds as a rule feed on soft fruits, such as figs, and bananas. It is to Acrulocercus, one of the Hawaiian genera of the Meliphagidæ, that Mr. Perkins refers me, on my asking him to name some of the fruit-eaters in that group.

These climbing shrubs, as Dr. Warburg observes, mostly frequent the tropical forests up to 4,000 feet and over. Though their most familiar habit is as tree-climbers in the forests, in localities where there are no trees they adopt a trailing habit and cover mountain peaks and ridges with a dense growth to the exclusion of almost all other plants. Many a peak in the Pacific islands would be inaccessible if it were not for the dense growth of these plants on their precipitous sides. It was owing to the friendly aid of a tangled mass of Freycinetia stems that Lieutenant Heming and myself were able to clamber to the summit of Fauro Island (1,900 feet) in the Solomon Group, where I discovered a tree that under the name of Sararanga forms the type of the third genus of the Pandanaceæ.

Whilst describing their station, it will be of interest to also record the altitudes at which these plants have been observed in the tropical Pacific. Since they can be independent of trees and are as much at home on treeless rocky peaks and mountain crests, the upper limit would usually be determined by climatic conditions, abundance of rain and great humidity being the chief requisites; but, as will be seen below, this limit does not seem to be reached in the tropical islands of the South Pacific except perhaps in Tahiti. In the Fijis the Freycinetias ascend to the highest mountain peaks. Thus, three of the species discovered here by Seemann were found at elevations of about 4,000 feet on Voma Peak in Viti Levu and in the highlands of Taviuni. In Vanua Levu, as I found, they cover the highest peaks 3,500 feet above the sea. They are especially abundant on the lofty mountain ridges, and clothe the higher slopes of the Mbatini Ridge which terminates in the highest peak of the island. In no locality did I find them growing in such densely tangled masses as on the long ridge-like crest that forms the upper part of Mount Freeland, 2,740 feet above the sea. For more than an hour in order to reach the summit I had to clamber along the crest of a ridge covered with a dense growth several feet deep of these trailing plants, without touching the ground beneath.

In Samoa, as we learn from Reinecke, Freycinetias are common on the mountain ridges, climbing the trees and forming also a dense undergrowth covering the ground and concealing the rocks. They occur at all levels from 1,000 feet above the sea up to the highest region of Savaii, rather over 5,000 feet in elevation. In Rarotonga, according to Mr. Cheeseman, the Freycinetias are very abundant on the mountains, which reach a height of 2,200 feet, the plants scrambling up the trunks of trees or over rocks and frequently rendering the forest almost impenetrable. In Tahiti, Nadeaud tells us, the Freycinetias often cover in an inextricable network the sides of the valleys at elevations of 2,000 to 3,300 feet, extending in their vertical range from the lower levels of the island to the highest inaccessible peaks which attain a maximum height of about 7,300 feet.

These plants in the Hawaiian group are common in the lower woods as Hillebrand informs us, that is to say, at elevations of 2,000 or 3,000 feet. During my descent from Mauna Kea through the Hamakua forests on the north-east side I observed that the Freycinetias commenced at an altitude of 3,900 feet, and that they attained their greatest development between 3,200 and 2,000 feet. These plants ascended quite a thousand feet higher on these mountain slopes than the Bird’s Nest Fern (Asplenium Nidus), which reached an altitude of 2,800 feet. In the forests on the west side of Mauna Loa they were abundant at altitudes of 3,500 to 4,000 feet and were not noticed above 4,500 feet. On the slopes of Mount Eeka in West Maui they abounded between 3,500 and 4,400 feet. In those localities where the forest descends to the sea, Freycinetias occur at the coast, and on Oahu they are often found at elevations under a thousand feet.

I have but few data showing the altitude obtained by Freycinetias in other regions, as, for instance, in their most southerly habitat in New Zealand, where they give a tropical luxuriance to the forests, or in their chief home in Malaya. From Schimper’s observations (_Plant-Geography_, p. 293) it would seem that they thrive in the Gedeh forest of Java at elevations of about 5,000 feet. Except for the lower levels, Warburg makes but few references to this subject in dealing with the species. It appears to me that some very interesting results might be obtained by comparing the vertical range of this genus in different regions, as, for instance, in New Zealand and in Borneo or in Java. We might get indications that since the age of Freycinetia began the climate in tropical latitudes has been getting warmer, and that the erstwhile plants of the lower levels are now as a result climbing the mountain slopes. The student of distribution may find here a genus that has been “cornered” not only in space and time, but as regards its conditions of existence. Since it is obvious that during a gradual increase of temperature it would ascend the mountains and during a lowering of temperature it would descend to the plains, it follows that in the mountains of an oceanic island it might be driven into the sea or await extinction on a mountain-top. In the tropics also there would be no escape during a gradual increase of temperature. Here again it would make its last stand on the strand, and, forced to choose between Death and Adaptation, the genus might select the latter alternative and present us with a startling new form. In this sense Freycinetia seems to offer itself as “fair game” for the speculative botanist, and at all events he will be able to interrogate it as to the connection between its existing range of altitude and the climatic conditions of the earlier phases of its history.

The Freycinetias bear the same name over Polynesia, “ie-ie” in Hawaii, “ie” and “ie-ie” in Tahiti and Samoa, which appear in their full form in the Rarotongan and Maori “kie-kie.” The secret of the wide distribution of the name lies in the circumstance that this is a mat-word over much of Polynesia, as in Fiji, Tonga, Samoa, the Gilbert group, Tahiti, &c., Freycinetia leaves being often employed for making mats, as in Samoa and New Zealand. The same word is applied in some groups to small species of Pandanus that were also used in mat-making. Thus in Fiji “kie-kie” was not only the name for a mat-dress, but also of Pandanus caricosus that supplied the material. In the home of the Polynesians in Malaya and its vicinity the same word for mat and Pandanus occur. Thus, “gerekere” in the Motu dialect of New Guinea and “keker” or “kekel” in Amboyna are the names of small species of Pandanus employed in mat-manufacture; whilst “kihu” and “kiel” in Celebes are the words for the mats themselves. Therefore in one form or another the word, originally applied to the mats, but now often restricted to the plants from which the materials were derived, ranges over the great region extending from Malaya to New Zealand, Tahiti, and Hawaii, and, as I have shown in the table given in my paper on Polynesian Plant-Names (_Journ. Victor. Inst._, London, 1896), it may be traced even to Further India, as in Annam, and to North-East Australia. It thus covers the area to which the migrations of the Polynesians of the Pacific have been confined, and it covers also the area of the genus Freycinetia. There is something far more than mere analogy between man and plants in their occupation of the Pacific islands. The plants are Malayan and the Polynesians are from Malaya also, whilst in both man and plants we experience the same difficulty in explaining their dispersal over the ocean. Divesting his mind of all previous conceptions, the ethnologist might profitably study _de novo_ the dispersion of man in the Pacific from the standpoint of plant-dispersal (see Chapter XXVIII).

SAPINDUS AND PHYLLANTHUS.

Brief reference can alone be made to these two genera. Foremost comes Sapindus, which is represented by two endemic species, one in Hawaii and one in Fiji, and by another species, found in Tahiti, the Marquesas, and Easter Island, which is identified by some botanists with the well-known American “soap-tree,” S. saponaria. There are several difficulties connected with the presence of this genus of the Old and New World in the Pacific. Not the least of them is connected with the transport of the large seeds of this genus, an inch in size, to the isolated Hawaiian Group, where it is represented by a solitary endemic species in the island of Oahu. The fleshy mesocarp of the fruits might attract birds; but it is not easy to perceive how birds could carry such large seeds over some 1,500 or 2,000 miles of ocean. Yet the same difficulty exists with a few other genera, such as Osmanthus and Sideroxylon, that are only represented in Hawaii by endemic species, genera which require the agency of birds to explain their occurrence unless we wish to postulate a continental connection for this group. (See under those genera in