CHAPTER XXIV

THE MOUNTAIN-FLORAS OF THE TAHITIAN AND FIJIAN REGIONS

The mountain-flora of the Tahitian region, as illustrated by the non-endemic genera.—Derived chiefly from high southern latitudes.—Weinmannia, Coprosma, Vaccinium, Astelia, Coriaria, Cyathodes, Nertera depressa, Luzula campestris.—The mountain flora of Rarotonga.—The mountain-flora of the Fijian region, as illustrated by the non-endemic genera.—Weinmannia, Lagenophora, Coprosma, Astelia, Vaccinium, Nertera depressa.—The Fijian Coniferæ.—Dammara, Podocarpus, Dacrydium.—Not belonging to the present era of dispersal.—The age of dispersal of the Coniferæ in the Pacific.—Earlier than the age of Compositæ and Lobeliaceæ.—The first in the Mesozoic period.—The last in the Tertiary period.—Summary.

THE MOUNTAIN-FLORA OF THE TAHITIAN REGION AS ILLUSTRATED BY THE NON-ENDEMIC GENERA

THIS floral region of the Pacific corresponds with the limits of Eastern Polynesia, and includes not only the Tahitian group proper, but also the Cook, Austral, Paumotuan, and Marquesan groups. It is only, however, in Tahiti, the peaks of which rise to over 7,000 feet above the sea, that we should expect to find such a mountain-flora, since the islands of the other groups are much lower, the highest of them in the Marquesan group barely exceeding 4,000 feet. Yet even in Tahiti it is not possible to speak of a mountain-flora in the sense that we attach to it in Hawaii. The elevated area of its interior is, as described in Chapter XIX., relatively very small; whilst, as Drake del Castillo points out, the conditions presented by the steep mountain-slopes rarely afford a hold for trees of any size, ferns often predominating in the higher levels. Still, we can observe the traces of such a flora, and it is in this sense only that the term “mountain-genera” is used in relation with this group.

_Mountain-Genera of the Tahitian or East Polynesian Region._

Weinmannia, Saxifragaceæ, from New Zealand. } Coprosma, Rubiaceæ, from New Zealand. }all species Vaccinium, Vacciniaceæ, from the northern hemisphere. }endemic. Astelia, Liliaceæ, from New Zealand. }

Coriaria, Coriariaceæ, from New Zealand }some Cyathodes, Epacridaceæ, from New Zealand }species }endemic

Nertera depressa, Rubiaceæ, a species of the Antarctic flora. Luzula campestris, Juncaceæ, from the northern hemisphere.

The Tahitian non-endemic mountain-genera, though scanty in number, are of considerable interest to the student of plant-dispersal. Among those possessing only species that are confined to Eastern Polynesia, genera that would be regarded as belonging to a past era of dispersal, Weinmannia, Coprosma, Vaccinium, and Astelia may be mentioned.

Weinmannia, a Saxifragaceous genus of trees and shrubs, not represented in Hawaii, but recorded from almost all the elevated oceanic groups of the tropical South Pacific, as well as from the New Hebrides and New Caledonia, has its home in South America, more particularly in the Andes, and also occurs in New Zealand, Tasmania, and the Mascarene Islands. One can scarcely doubt that, as in the case of Coprosma, the Pacific Islands derived their species originally from high southern latitudes, as from New Zealand, the absence of the genus from Hawaii negativing an American origin. Of the two Tahitian species, one is peculiar to Tahiti, whilst the other, W. parviflora, which is conspicuous on the mountain-crests at elevations of 3,000 feet and over, occurs also in the Marquesas. Another species grows in abundance in the interior of Rarotonga. Samoa possesses two species, one of which, W. affinis, occurs in Fiji, and the other, W. samoensis, which frequents the mountains at elevations of 1,500 to 3,300 feet, is seemingly endemic. Fiji possesses four or five species of Weinmannia occurring at all altitudes up to 2,000 feet, of which some are evidently peculiar. The capsular fruits of this genus contain hairy seeds that would probably become entangled in a bird’s plumage. Dispersal by birds is distinctedly indicated in the curious observation of Dr. Reinecke in the case of the Samoan peculiar species. The seeds, he says, appear to germinate by preference on the bark of other trees, young plants growing epiphytically being of frequent occurrence.

There is some evidence that the species of Weinmannia, about ten in all, found in the tropical islands of the open Pacific are derived from one or two polymorphous species. As we learn from Mr. Cheeseman, the Rarotongan species, W. rarotongensis, has considerable affinity to several closely allied Polynesian species, and its nearest allies are a Fijian and Samoan species, W. vitiensis and W. samoensis. Possibly, he remarks, fuller materials may lead to the union of several of these forms under one species.

The interesting New Zealand genus Coprosma, which we have noticed in Hawaii, occurs also in the Tahitian region and Fiji; and it will be further discussed under the last-named locality. The genus Vaccinium has been previously dealt with in Chapter XXIII.

The Liliaceous genus Astelia may be considered as representing, like Coprosma, the Antarctic or New Zealand flora in the higher levels (usually) of the islands of the tropical Pacific, where it grows both on trees and on the ground. The genus, according to Hemsley, is chiefly at home in New Zealand, but is also found in Fuegia and in South-east Australia. It is represented in Hawaii, Tahiti, Samoa, and Fiji. In Hawaii there are two peculiar species ranging between 2,000 to 6,000 feet in elevation. The solitary Tahitian species, A. nadeaudi, is found in the central mountains of Tahiti, reaching to the crests of Mount Aorai, which attains a height of 6,700 feet. Fiji and Samoa possess a species in common, A. montana, which is only recorded by Seemann, from the summit of Kandavu, 2,750 feet above the sea; whilst in Samoa it frequents, according to Reinecke, moist coast districts. The fruits of Astelia are berries with crustaceous seeds that would be dispersed by frugivorous birds.

Amongst the Tahitian mountain-genera that possess species ranging far beyond this region as well as species confined to the group may be mentioned Coriaria and Cyathodes. It is to their non-endemic species that we look for further clues as to the general lines of migration by which the mountain-genera that only possess peculiar species reached this group. The evidence afforded by Coriaria is of some importance. The genus has not been recorded from Hawaii, and, so far as the collections of Seemann and Home show, not from Fiji. It is found in the Mediterranean region, the Himalayas, Japan, New Zealand, and Antarctic America, including Chile; and there are two particular species, C. ruscifolia and C. thymifolia, that occur in both cases in New Zealand and the adjacent islands and in South America (Introd. _Chall. Bot._ p. 53). The first of these, which is very common in Chile, exists also in Tahiti on the crest of Aorai, 6,700 feet above the sea. Drake del Castillo also describes a peculiar Tahitian species, C. vescoi, of which the altitude is not given. Here one is in doubt whether Tahiti derived its wide-ranging species from New Zealand or from Chile; but in the New Zealand home of Coprosma, another Tahitian mountain-genus, we are afforded the clue. The fruits of Coriaria possess fleshy cocci that attract birds, though it would seem that the seeds of plants of this genus are poisonous for man. Among the numerous fruits that form the diet of the New Zealand fruit-pigeon (Carpophaga novæ zealandiæ) are included, as we learn from Sir W. Buller in his _Birds of New Zealand_, those of the “tupakihi” or “tutu” shrub, which Kirk identifies with C. ruscifolia, the species that also occurs on the summit of Tahiti.

The Australian and New Zealand genus Cyathodes (Epacridaceæ) has been already noticed in the case of Hawaii (page 282). The two Tahitian species occur on the elevated mountain-ridges forming the summits of Tahiti, one of them, C. tameiameiæ, occurring also in Hawaii, and the other, C. pomaræ, being restricted to the group. I have shown that the fruits are dispersed by frugivorous birds, and I can only include the genus as another example of the representation of the New Zealand flora in Tahiti.... There remain of these so-called Tahitian mountain-genera the Antarctic Nertera and the north-temperate Luzula, each represented by a solitary widely ranging species, N. depressa and L. campestris, which I have fully discussed under Hawaii (Chapter XXIII), in which group they also occur.

When we look at the evidence of origin supplied by the four Tahitian mountain-genera possessing species that are found outside the group, namely Coriaria, Cyathodes, Nertera, and Luzula, we find that the first three hail from high southern latitudes, and more especially from New Zealand; and when with this clue in our hands we take up the four genera Weinmannia, Coprosma, Vaccinium, and Astelia, possessing only species restricted to the Tahitian region, we find that all but the third-named genus hail also from the south. It would thus appear that the element of the Antarctic flora is much more evident in the Tahitian mountain-genera than with those of Hawaii. In the Hawaiian mountain-flora, excluding, of course, the endemic genera, it includes about a fourth of the mountain-genera, which number about thirty-eight or forty in all; whilst in the Tahitian mountain-flora it comprises six out of the eight genera. It may, indeed, be said that the resemblance between the mountain-genera of Hawaii and Tahiti is mainly restricted to genera that are found in high southern latitudes, namely, Nertera, Coprosma, Cyathodes, and Astelia, the only other genera linking the mountain-floras of both groups together being Vaccinium and Luzula, which probably hail from high northern latitudes. The agency of the frugivorous bird is plainly marked in the case of five out of the six genera that connect the cloud-capped peaks of Tahiti and Hawaii. In two of these genera, Cyathodes and Nertera, the same species occurs in both archipelagoes.

_The Mountain-flora of Rarotonga._—A word may here be said on the representation of these mountain-genera in Rarotonga, a small island 2,250 feet in height and about eight miles in length, which is, however, the most important island of the Cook group. The recent important explorations of Mr. Cheeseman show that its flora is essentially Tahitian in character. As in Tahiti, the early age of the Compositæ and Lobeliaceæ is well represented in the high levels by peculiar species of Fitchia and Sclerotheca which are discussed in Chapters XXI and XXII. On account, however, of its relatively low altitude and its small size, we could not expect any extensive representation of the eight non-endemic mountain-genera of Tahiti. Yet three of these occur, a Tahitian species of Vaccinium (page 281) growing on its summits, whilst peculiar species of Weinmannia (page 290) and Coprosma (page 295) are found in its interior. The prevailing condition of many of the genera growing in the higher levels is one of isolation, since other genera, like Pittosporum and Elæocarpus, only possess peculiar species; but seeing that in several cases the species are closely allied to others found in the Western Pacific, as in Samoa, Fiji, and the Kermadec group, it is apparent that the period of isolation has not long commenced.

THE MOUNTAIN-FLORA OF THE FIJIAN REGION.

Weinmannia, Saxifragaceæ, Fiji and Samoa. } Derived from Lagenophora, Compositæ, Fiji. } New Zealand or Coprosma, Rubiaceæ, Fiji. } from the Astelia, Liliaceæ, Fiji and Samoa. } Antarctic flora.

Vaccinium, Vacciniaceæ, Samoa, from the northern hemisphere. Nertera depressa, Rubiaceæ, Samoa, from the Antarctic flora.

Dammara, Coniferæ, Fiji. }Not as a rule belonging Podocarpus, Coniferæ, Fiji and Tonga. }to the present age Dacrydium, Coniferæ, Fiji. }of dispersal

But little can be said of the mountain-flora of Fiji, since on account of the relatively low elevation of the islands there are but few special mountain-genera; and as a rule we find only here and there a solitary species on some isolated peak that recalls the upland flora of the Hawaiian mountains. “None of the mountains of Fiji,” remarks Horne (page 60), “are high enough for an alpine flora to exist. Many of the plants found on the tops of the mountains are also found near the level of the sea. On the other hand sea-level plants may also be found on the tops of the hills.”

Fiji lacks the endemic genera of Compositæ and of Lobeliaceæ that often give a character to the mountain-floras of the Hawaiian and Tahitian regions, though, as remarked in Chapters XXI and XXII., their absence involves something more than a question of station. We find, however, four genera of the Antarctic or New Zealand flora, Weinmannia, Lagenophora, Coprosma, and Astelia. The first-named genus possesses four or five species ranging up to 2,000 feet, some of which are endemic, and it has been already discussed in this chapter. The United States Exploring Expedition found a single species of Lagenophora (L. pickeringii) on the mountains of the Mathuata coast of Vanua Levu, and no other species seems to have since been found. The subject is dealt with in Chapter XXIII in the case of Hawaii, but it may be here observed that there is an Hawaiian mountain species, and that the route followed by the ancestor of the Fijian species from the New Zealand home of the genus is indicated by a species in the intermediate Kermadec group. The genus Astelia has been discussed on page 291. It is represented in Hawaii and in most of the oceanic groups of elevated islands. The solitary species, A. montana, discovered by Seemann on the summit of Kandavu in Fiji, has since been found in Samoa, and probably Mr. Horne’s collections contain another species.

The Rubiaceous genus Coprosma needs a few special remarks, since a particular genus of birds seems to have been concerned in dispersing it in the South Pacific. About fifty species are enumerated in the _Index Kewensis_, and if we include a few other species from the collections of Hillebrand, Horne, Cheeseman, &c., the total would be about sixty. Of these, about half are restricted to New Zealand, which may be justly regarded as the home of the genus, the rest being confined to Australia and the islands of the Pacific, excepting a Chilian and three or four Malayan species. Hawaii with its nine species, Tahiti with two, Rarotonga with one, and Fiji with two or three species represent approximately the distribution of the genus in the oceanic archipelagoes of the tropical Pacific. (It most probably exists on the high peaks of Samoa, though it has not yet been recorded from the group.) In all, or in almost all cases, the species are restricted to their particular groups, so that we may regard the dispersal of the genus over the Pacific as suspended, though, as will be observed below, the period of suspension in the South Pacific has not been of sufficient duration to obliterate the affinities of species in distant groups and to prevent us from tracing out the route followed by the genus.

This genus of temperate latitudes, which in its New Zealand home ranges from near the sea-level to the region of the alpine floras, finds its usual station in the tropics on the summits of mountains. Thus, on Mount Kinabalu, in Borneo, it is found at altitudes of 10,500 to 13,000 feet (Stapf), and on the mountains of East Java at elevations exceeding 9,000 feet (Schimper). In Hawaii its species grow at elevations ranging from 3,000 to 9,000 feet, and in Tahiti at altitudes of 2,600 to 3,300 feet; whilst in Rarotonga it grows in the hilly parts of the island, its elevation in Fiji not being recorded.

When we come to consider the route by which the genus (Coprosma) entered the tropical Pacific, we must remember that unless we establish some special connection with its New Zealand home it will always be open for any one to suggest that the genus might have been derived, like Vaccinium, from other regions than the south, as from the summits of the Malayan mountains. However, a curious connection has been discovered by Mr. Cheeseman in his examination of the Kermadec and Rarotongan floras, and it would indeed appear that he has traced the Rarotongan peculiar species to its New Zealand home. Thus, he says that Coprosma lævigata, his new Rarotongan species, is very closely allied to the Kermadec endemic plant, C. acutifolia, Hook., which itself comes near C. lucida, Forst., a New Zealand species. The connection between Rarotonga and New Zealand by way of the Kermadec group is rendered yet more probable by the occurrence of two New Zealand species of Coprosma in the Kermadec flora (_Journ. Linn. Soc._ i. 1857; _Trans. Linn. Soc. Bot._ vi. 1903; _Trans. N.Z. Instit._ xx. 1887).

When speaking of the genus in Hawaii (page 275), mention was made of the inter-island dispersal of the fruits of one of the species by the native mountain-goose, Bernicla sandwicensis. We learn from Sir W. Buller’s _History of the Birds of New Zealand_ that when the Coprosma is in fruit the Swamp-Hens (Porphyrio melanotus) come out to feed on it. These birds, he says, are capable of prolonged flight; and I chance to have beside me a cutting from the _Field_ of July 9, 1904, in which “Hy. S.” refers to a Black-backed Porphyrio that was captured in 1876 four hundred miles off the coast of New Zealand. This genus, which is widely dispersed in the tropics, the birds being commonly known as Sultanas, Blue Gallinules, Purple Water-Hens, &c., has probably been a very important factor in the dispersal of plants, especially in connection with insular floras. The birds live on a variety of food. The Messrs. Layard observed that Porphyrio vitiensis, which abounds in the swamps of New Caledonia, fed on maize, yams, &c. (_Ibis_, 1882); whilst in the stomach of a bird of the same genus shot in the Rewa swamps in Fiji I found a number of the stony fruits of Scleria, a genus of the Cyperaceæ. According to Mr. Wiglesworth, each region in the South Pacific has its own species of Porphyrio. There is one in the Tahitian Islands, and another common to Fiji, Tonga, and Samoa; whilst New Caledonia and the New Hebrides have their species (“Aves Polynesiæ”). However, it is evident that the power of dispersing seeds from group to group is not quite suspended, since, as we learn from Sir W. Buller, the New Zealand species, above named as partial to Coprosma drupes, is distributed over Tasmania and Australia, and reaches also Niue and New Caledonia; whilst the Messrs. Layard evidently regarded one species as common to Fiji and New Caledonia.

It is doubtless to birds of this description that we owe some of the specific connections of Coprosma between groups of the Western Pacific. That the dispersal of the species over distant regions was recently in active operation is shown by the close affinity, according to Dr. Stapf, of two species growing on the summit of Kinabalu, the Bornean mountain, with certain species from New Zealand and South-east Australia. Other Rubiaceous species, like Nertera depressa, possessing Coprosma-like fruits and fitted for the same mode of dispersal, link the heights of Kinabalu with the flora of high southern latitudes.

Being included in the Fijian area, the scanty mountain-flora of Samoa may be here referred to. As in Fiji, the endemic genera of Compositæ and Lobeliaceæ are not to be found, but we find in the central elevated district of Savaii, which rises to over 5,000 feet above the sea, a peculiar species of Vaccinium (4,900 feet), the Antarctic Nertera depressa (4,000 feet), and two species of Weinmannia, a genus hailing probably from high southern latitudes.

THE FIJIAN CONIFERÆ.

It has been found most convenient to discuss here these interesting plants, which belong in a general sense to the mountain-flora of this archipelago. That which the Fijian flora loses in interest in the eyes of the student of plant-dispersal in not possessing the mysterious Composite and Lobeliaceous genera of Hawaii and Tahiti, it regains in the possession of its genera of Coniferæ. If he felt loth to apply his empirical principles to the above-named Hawaiian and Tahitian endemic genera, he feels more than uneasy when he comes to deal with the three Coniferous genera of Fiji, Dammara (Agathis), Podocarpus, and Dacrydium.

These three genera represent an order that has not found a home either in Tahiti or in East Polynesia generally, or in the more distant Hawaii; and they present at first sight in their existence in Fiji a powerful argument in favour of the previous continental condition of the islands of the Western Pacific. But in advocating this view we should remember that it involves the original continuity of the Fijian land-area, not only with the neighbouring islands of the New Hebrides and of New Caledonia where these genera alike occur, but also with New Zealand, Tasmania, and Australia, where they sometimes attain a great development.

In Fiji these trees often chiefly form the forests of the larger islands, extending in the moister regions from near the sea to the mountain-tops, and being often abundant on the great mountain-ridges of the interior. It may be at once remarked that, viewed merely from the standpoint of dispersal, there is no great difficulty in regarding it as probable that the seeds of Podocarpus and Dacrydium have been dispersed by frugivorous birds over tracts of ocean 500 or 600 miles across. Dammara, however, so far as my Fijian observations show, possesses none of the means of dispersal across oceans that we are at present acquainted with. The two first-named genera occur in South America as well as in the Australo-Polynesian region, some of the species in these two regions, though the Pacific Ocean divides them, being closely related. Dammara is, on the other hand, confined to a much more limited area, extending from New Zealand to Borneo. It is from the distribution of this genus that the continental theory derives its chief support.

Yet it may be remarked that something more than questions relating to the capacity for dispersal are involved here. This is at once indicated by the circumstance that although Podocarpus is known to be dispersed by frugivorous birds, it is not found in Polynesia east of Tonga, and the same may be said of Dacrydium, which does not occur east of Fiji. In this connection it is necessary to notice the intrusion of Araucaria into the tropical Pacific from Eastern Australia to New Caledonia and the New Hebrides. The fact of this genus not having been recorded from Fiji or any of the groups east of the New Hebrides is very remarkable, and scarcely in accordance with the continental hypothesis. There is a persistence in type of these genera of the Coniferæ during geological time that prevents us from dealing with them on the lines that are required by the mass of the flowering-plants. Other factors intervene, and we apply with hesitation the same canons of dispersal that we employ for the general bulk of the plants of the Pacific islands. If, as often happens, a specific distinction alone separates the Conifers of the same genus on either side of the Pacific Ocean, it must possess in point of time a very different value from that which we would usually attach to specific distinctions in the floras of the Pacific islands.

DAMMARA (AGATHIS).—The Dammara region includes Eastern Australia, New Zealand, New Caledonia, with the New Hebrides, Fijian, and Santa Cruz groups, and extends north-west to Java and Borneo. Only ten species are named in the _Index Kewensis_, and of these four are assigned to New Caledonia and two to Fiji, the focus of geographical distribution being, therefore, as Seemann long since pointed out, in the islands of the Western Pacific. The absence of the genus from the neighbouring Samoan and Tongan groups is very significant; and it is evident that the ordinary agencies of dispersal, whether birds, winds, or currents, have here failed to extend the genus over a few hundred miles of sea.

When by means of observation and experiment we turn to the fruits and look for a reply, we find in the first place that they are never to be noticed either whole or in part in the floating drift of sea or river, or amongst the stranded materials of the beaches. This is at once explained when we ascertain that the fresh cones sink in the river-water, and thus could never reach the coast in their entire condition. Nor could they do so in fragments, since the detached cone falls to pieces on the ground and the separate scales and seeds sink at once or float only for a few hours. In order to test the buoyancy of a cone after drying, it is necessary to bind it round with string to keep it from breaking down. One such fruit, after being kept for ten days, was placed in sea-water, where it floated heavily for eleven days and then sank. This is, of course, a most unnatural experiment, but it was well to have carried it out. That the entire fruit could never be transported by water is indirectly implied by Kirk respecting the fruit of Dammara australis, the Kauri Pine of New Zealand. In this case, when the fruit reaches maturity the scales, he remarks, fall away from the woody axis of the cone and the seeds are freed.

The fleshy, unprotected seeds, which, as above noted, possess little or no floating power, could scarcely withstand the injurious effect of sea-water; and they are absolutely unfitted for any known mode of dispersal by birds. It is observed by Kirk that the seeds of the New Zealand tree are widely spread by winds. But this could only avail them for local dispersion, and they appear ill-suited for being transported for more than a few paces. The seeds are winged, and are in form a little like the samara of the Maple (Acer); but they have not the same protective coverings, the wing being, however, only a little more than half the length of the entire seed. Those of both Dammara australis and D. vitiensis are about two-thirds of an inch in length, and are heavy-looking; and the agency of the wind could never be invoked except for local dispersion.

Looking at these results, the cones of Dammara may be regarded as most unsuited for any of the ordinary means of dispersal over an ocean except through the agency of man. There is, however, no necessity to introduce man’s aid here, unless the gum or resin which the Fijian burns in his torches and employs as a glaze for his pottery gave his ancestors an object in carrying the cones with them in their migrations. But in that case the same argument would have to be applied to all partially useful plants, and much of the Fijian flora would lose its indigenous reputation. The endemic character of the Fijian species also militates against such a view, and we should have to apply the same explanation to the New Zealand species, concerning which no one, so far as I know, has ever ventured to suggest that it was introduced by the Maoris.

The native names of the trees seem to have been sometimes connected with general words for gums or resins; whilst at other times the tree and the resin have separate designations. Thus the Fijians call the tree “ndakua” and the resin “makandre,” which last Hazlewood in his dictionary seemingly connects with “ndrenga,” the word for “gum.” In my work on the Solomon Islands, page 190, I have endeavoured to show that the Maori name of “kauri” may be connected with “gatah,” the general Malayan word for gums and resins, transitional stages being presented in the names of resin-yielding trees in the intermediate regions, as, for instance, by “gutur,” a species of Canarium, on the Maclay coast of New Guinea, and by “katari,” a species of Calophyllum, in Bougainville Straits, Solomon group. It may be pointed out that these facts of plant-nomenclature do not promise us any aid in determining the mode of dispersion of Dammara in the Western Pacific. There is a suspicious resemblance between the Fijian name of “ndakua” and “dundathu,” the Queensland aboriginal name for Dammara robusta; but even if the comparison is legitimate, its explanation may lie far back in the ages in some root-word as ancient as the Malayan “gatah.”

If there is a real difficulty in applying our canons of plant-dispersal to the distribution of Dammara, it is merely the same difficulty that has so often perplexed the botanist with other Coniferous genera in continental regions, such as, for instance, the occurrence of Pinus excelsa on the far-removed mountains of Europe and of the Himalayas, and the existence of the cedar in its isolated homes on the Atlas, the Lebanon mountains, and the Himalayas. Such difficulties largely disappear if we regard the present distribution of the Coniferæ as the remnant of what it was in an ancient geological period. In the case of Dammara it seems almost as idle to puzzle over its means of dispersal as to consider the mode of dispersal of the Marsupials. The questions, indeed, that affect the Dammaras of Fiji and the Western Pacific far ante-date any questions concerning a previous continental condition of those regions. The attitude of the palæobotanist to such questions would probably be one of indifference; yet to the student of plant-distribution they are of prime importance; and _nolens volens_ we must admit that Dammara may well be cited in support of any continental hypothesis affecting the Western Pacific.

PODOCARPUS.—In this connection I will mainly depend on Pilger’s recent monograph on the Taxaceæ (heft 18, Engler’s _Das Pflanzenreich_, 1903). More than sixty species are here enumerated, which are distributed in Africa, Asia, Australasia, and South America. With a range that extends north to Japan and south to Southern Chile in latitude 48°, this genus attains its greatest development in respect of species in Malaya, in the region comprised by Australia, New Zealand, and New Caledonia, in South America, and in Africa. Eastward of New Caledonia it is found in Fiji and in Tonga, but not in Samoa, and it is altogether absent from the Tahitian region as well as from Hawaii. Of the four species accredited by Seemann to Fiji, two are enumerated by Pilger, namely, P. affinis and P. vitiensis. The first-named, according to Stapf, is allied to P. bracteata, which occurs on the upper slopes of Kinabalu, in Borneo, and is distributed not only over Malaya, but occurs in Japan and in the Himalayas. The Tongan species, P. elatus, is, according to Hemsley, found in East Australia.

This Tongan tree is suggestive of bird-agency in the dispersal of the genus, and the same may be said of the occurrence of another species, P. ferrugineus, found in both New Caledonia and New Zealand. Since the seeds of the genus possess an outer fleshy and an inner bony covering, they would appear to be well fitted both to attract and to be dispersed by birds. In fact, we learn from Sir W. Buller that the New Zealand fruit-pigeon feeds on the seeds of the “matai” tree (Podocarpus spicata) and of the “kahikatea” (P. dacrydioides), and no doubt to the agency of frugivorous birds we can attribute the presence of the genus in Fiji and Tonga. Yet it is strange that bird-agency should have failed both with Tahiti and Hawaii. In point of size the seeds, which range from one-quarter to an inch across, present no great difficulty, and one would have thought that the birds that carried the “stones” of Elæocarpus to Hawaii could have also carried the seeds of Podocarpus.

It is, however, necessary to remember, in dealing with a genus that has a wide distribution both in time and space, that specific affinities may have a very different significance with the Gymnosperms than with most other flowering plants. When Hemsley remarks (_Introd. Chall. Bot._ p. 56) that the New Zealand Podocarpus spicata is closely allied to the South American P. andina, he does not imply that the two regions are in touch with each other though some 5,000 to 6,000 miles of ocean intervene. One is prepared to credit these seeds with a capacity of dispersal by birds over tracts of sea such as the extent of ocean separating New Caledonia and New Zealand, which are some 900 miles apart; but one hesitates to admit that frugivorous birds could carry them across the Southern Ocean. If we assign a home in the high latitudes of the northern hemisphere to a genus that was well represented in Europe in the Tertiary period, a movement of migration southward would explain most of the difficulties in its present distribution. The great vertical range of some of the species leads us to attribute a corresponding power of adaptation to the genus in respect of widely different climates. Thus, according to Stapf, the vertical range of P. bracteata in the Malay Archipelago extends, including varieties, from the coast to an altitude of 12,000 feet. With such a capacity for adaptation, migrations of the genus would be rendered easy over the globe.

DACRYDIUM.—It may happen that some additional light on the mystery of the Fijian Coniferæ may be afforded by Dacrydium elatum, a tree that occurs not only in Fiji, but in Further India and in Malaya. Pilger confirms Seemann’s view in his identification of the Fijian tree, and this opinion is, in the main, shared by Stapf. This species, so to speak, affords us a _point d’appui_ in the history of the distribution of the genus in the Western Pacific. This distribution somewhat resembles that of Dammara in extending from New Zealand (its principal centre) to Malaya and Further India; but, unlike Dammara, Dacrydium is represented in America by a solitary species in South Chile. Of the sixteen species enumerated by Pilger, seven belong to New Zealand, four to New Caledonia, three to Malaya, one to Tasmania, and one to Chile. The seeds are, as a rule, smaller than those of Podocarpus, and on account of their somewhat similar structure would serve as bird-food, and might be distributed in this fashion. Yet the genus has been only recorded from Fiji, and is not only unrepresented in Hawaii and Tahiti, but is also not known from the Tongan and Samoan groups that belong to the Fijian floral region of the Pacific. Capacities for dispersal appear meaningless here, especially when we have regard to the solitary American species, Dacrydium fonkii, that as a shrub finds a refuge in the bleak region of Southern Chile.

The three Fijian genera of the Coniferæ, Dammara, Podocarpus, and Dacrydium, appear at first sight to be beyond the reach of our canons of plant-dispersal, by which we connect specific affinity with a continuity of range, and by which we co-ordinate means of dispersal and area of distribution. We begin to realise that there may have been an age of Coniferæ in the Pacific islands that is even less amenable to our methods than the later era of the Compositæ and Lobeliaceæ in Hawaii and Tahiti. Such an age would be concerned only with that region in the Western Pacific which is now held by the genera Dammara, Podocarpus, and Dacrydium, a region that did not participate in the era of the Compositæ and Lobeliaceæ. We thus have evidence of an ancient era of the Coniferæ that was confined to the Western Pacific, and of a later era indicated by the peculiar genera of Compositæ and Lobeliaceæ that was restricted to Hawaii and to Eastern Polynesia (Tahiti, Rarotonga, &c.). The key to the situation here presented seems to lie in the following considerations.

It is assumed that there was an age of Coniferæ in the Pacific, or rather that this region shared in an era of dispersion of existing genera of the order. In this age only the islands of the Western Pacific participated, neither the Hawaiian nor the Tahitian islands taking a part in it. Such a result is to be attributed either to the inability of these genera of Conifers to reach Hawaii and the islands of East Polynesia, or to the non-existence of the Hawaiian and Tahitian archipelagoes at that epoch. The first explanation seems scarcely acceptable, since, although the powers of dispersal of the genus Dammara are very limited, there seems no reason why the genera Podocarpus and Dacrydium could not have reached those distant regions of the Pacific. The second explanation is most probable, and it is the one suggested by Hillebrand (p. xxx) in the case of Hawaii, namely, that “the absence of Gymnosperms militates for the view that the islands were formed subsequent to the age in which these were universally distributed.”

If this conclusion is legitimate we have here a datum-mark in the history of the islands of this ocean. Before the appearance of the Hawaiian and Tahitian islands (using the term Tahitian to cover the East Polynesian region) there existed a land-area in the Western Pacific held by the Coniferæ, probably in the late Secondary period. After the formation of the Hawaiian and Tahitian islands, perhaps in the early Tertiary epoch, came the age characterised by the ancestors of the present endemic genera of the Compositæ and Lobeliaceæ, and of a few other orders in Hawaii and Tahiti. In this age the islands of the Western Pacific do not seem to have participated, and it is to be inferred that this was an age of extensive but probably not of complete submergence in that part of the ocean, since at least the genus Dammara was able in places to hold its ground. Then ensued the great Tertiary emergence of the land-areas of the Western Pacific, when small islands that dotted the sea-surface in this region became the nuclei for the formation of the large islands of the present Fijian, New Hebrides, and Solomon groups. This prepared the way for the migration of Malayan plants which now predominate over the islands of the tropical Pacific; and in a later age man, following the same track from Indo-Malaya, occupied these islands.

In my volume on the geology of Vanua Levu it was shown that the Tertiary period was an age of submergence in the Western Pacific, and a disbelief in any previous continental condition was expressed. My later view is more in accordance with that of Wichmann, who, on geological grounds, contended that the islands of the Western Pacific were in a continental condition during the Palæozoic and Mesozoic periods, and that their submergence and subsequent emergence took place in Tertiary times. The distribution of the genus Dammara has thus led me to modify the views expressed in the final chapter of my first volume on the geology of Vanua Levu. Though still holding that there is no geological evidence that the various islands of the Fijian group were ever amalgamated, or that they were joined as such to the westward groups, it is quite possible that their position was indicated by a few small islands a few miles across and a few hundred feet in height in early Tertiary times. On these small islands, which probably represented the remains of a submerged Mesozoic land-area, such as is in part implied in Dr. Forbes’ _Antipodea_, or in Mr. Hedley’s _Melanesian Plateau_, the genus Dammara survived. Such islands merely indicated the situation of some of the present groups of the Western Pacific, which have been since largely built up by submarine eruptions, and the greater number of the islands were no doubt completely submerged. Between the groups as we know them now there never was any land connection, since they are the product of later eruptions, mainly submarine; and they have acquired their present composite character during the emergence that followed the period of volcanic activity. Except, perhaps, in New Caledonia, which does not seem to have shared in the Tertiary submergence, the islands of the Western Pacific have a configuration acquired in comparatively recent times, and one that gives no idea of the character of the Mesozoic continent.

Such, as I understand them, are the indications of the Fijian Coniferæ and particularly of Dammara. In the distribution of this genus we have outlined an ancient, more or less continuous land area which, with the exception of a few isolated points, disappeared beneath the sea in Tertiary times to re-appear near the close of that period in the form of a number of archipelagoes that were largely built up by submarine eruptions, and probably altogether mask the form of the original land-area. It may be remarked that New Zealand, which largely shared in the Tertiary submergence, especially in the Miocene age, is included in the range of the genus Dammara, as well as in those of the genera Podocarpus and Dacrydium.

_Summary._

(1) The evidences of a mountain-flora in Tahiti, as indicated by the non-endemic genera, though, as we would expect, of a scanty nature when contrasted with Hawaii, are nevertheless of considerable interest. There is much kinship with the Hawaiian mountain-flora, but it is mainly confined to genera from high southern latitudes, such as Nertera, Coprosma, Cyathodes, and Astelia, which are all dispersed by frugivorous birds. Amongst other plants linking the Tahitian mountains with the region of the Antarctic flora, and with New Zealand in particular, may be mentioned Coriaria ruscifolia and the genus Weinmannia.

(2) On account of their relatively low altitude the Fijian islands do not present the conditions for an alpine flora. Traces, however, of the Antarctic flora, or of the New Zealand flora, occur on occasional mountain-tops, as is indicated by the occurrence of species of Lagenophora, Coprosma, and Astelia. In Samoa the mountain-flora is also scantily developed, as we might have expected; but here occurs the genus Vaccinium as well as a widely-ranging species of the Antarctic flora, Nertera depressa.

(3) The route by which some of the representatives of the flora of high southern latitudes reached the mountains of the islands of the tropical Pacific is directly indicated by the genus Coprosma to have been from New Zealand by way of the Kermadec Islands.

(4) In the distribution of plants possessing drupes or berries that connect the tropical islands of the South Pacific with New Zealand, it is highly probable that birds of the genus Porphyrio (Swamp-Hens or Purple Water-Hens) have taken a prominent part.

(5) In the possession of species of the three genera of Coniferæ, Dammara, Podocarpus, and Dacrydium, which often largely form the forests of the mountain-slopes, Fiji is distinguished from all the other groups of the open Pacific with the exception of Tonga, which owns a species of Podocarpus probably introduced by birds. From the circumstance that Dammara has no known means of crossing a tract of ocean, whilst Podocarpus and Dacrydium could be dispersed by frugivorous birds, all three genera having, however, much the same limited distribution in the Western Pacific, it is apparent that something more than a question of means of dispersal is here involved. It is assumed that they mark the site of a Mesozoic continental area in this region, and that at this period the Tahitian and Hawaiian groups which possess no Conifers did not exist. This area was submerged during the Tertiary period with the exception of a few peaks that formed small islands on which the Conifers held their ground. During the Tertiary submergence of the Western Pacific region, the Hawaiian and Tahitian islands were built up by subaërial volcanoes and received the ancestors of the Compositæ and Lobeliaceæ that now exist as endemic genera in those groups. Then followed the emergence of the islands of the Western Pacific and their occupation mainly by Indo-Malayan plants that extended eastward over the Pacific. Thus in the Pacific there has been first an age of Conifers in which the islands of the Hawaiian and Tahitian regions could not participate, since they did not exist. Then ensued an era of American forms of Compositæ and Lobeliaceæ in which only Hawaii and Tahiti participated, since the Western Pacific region was submerged. Lastly came the invasion of Indo-Malayan plants, which have largely occupied every group in the tropical Pacific.