As far as the flora of the lower levels (below 4,000 feet) is concerned,

Hawaii only possesses a portion of that which Fiji has derived from the

Old World, chiefly through Malaya. Although, as will be shown below,

there is a noticeable contribution from America, it is very far from

counterbalancing the loss which the Hawaiian flora has sustained in

comparison with Fiji through the isolated position of the group. The

want of variety, however, in the flora of the Hawaiian lower levels,

which up to 4,000 or 5,000 feet represent the islands of the less

elevated Fijian region, is in a small degree compensated for by the

development of new genera and new species and by the great number of

individuals. Trees like Metrosideros polymorpha and Aleurites moluccana,

that in the southern groups form only one of many contributors to the

forests, rise suddenly into prominence in the northern archipelago and

form entire forests. Pandanus odoratissimus largely composes extensive

forests in the province of Puna in the large island of Hawaii, extending

several miles inland and nearly 2,000 feet up the mountain slopes.

The remarkable contrast between the Fijian flora, which is almost

entirely tropical, and the Hawaiian flora, which on account of the great

elevation of the islands is temperate as well as tropical, is brought

into yet greater prominence when we look at it more closely and treat it

numerically. The Hawaiian Group, it must be first observed, though

possessing the same area as Fiji and presenting a far greater variety of

climatic conditions, has only two-thirds the number of genera of

flowering plants (see Chapter XXI., Table B). Whilst at least 200 of the

Fijian genera of indigenous plants (excluding the orchids and the

grasses) are not found in Hawaii, only about 100 of the Hawaiian genera

are absent from Fiji, and the two groups possess about 100 genera in

common. When we look more closely at the hundred Hawaiian genera not

found in Fiji, we find that about sixty represent endemic genera

(thirty-seven) and non-endemic mountain-genera (twenty-two), which

naturally are not to be found in Fiji, so that there remain but a small

number of genera distinguishing the tropical flora of Hawaii from the

Fijian flora. When we take from them a few that occur in the Tahitian

region, there is left a very small residuum characteristic of Hawaii

alone to the exclusion of the Fijian and Tahitian regions of the South

Pacific.

THE HAWAIIAN RESIDUAL GENERA.

It is my purpose now to deal in an illustrative fashion with this

Hawaiian residual flora which is composed, as above explained, of the

non-endemic tropical genera that are not represented in the Fijian and

Tahitian regions. Up to the present we have been dealing with the

characters that the floras of Fiji, Tahiti, and Hawaii possess in common

as far as tropical genera are concerned. We will now proceed to discuss

their differences in this respect, and will begin with the residual

Hawaiian flora.

After eliminating two or three genera that will probably be found in

Fiji, but including one or two others that are best treated under the

endemic genera, about twenty-seven present themselves for our purpose.

Nearly all of them possess only endemic species, and belong therefore to

an age of dispersal that has passed away. These residual genera plainly

indicate that although Hawaii largely received its flora during the age

of general dispersal of Old World genera over the Pacific, it was at the

same time independently stocked with plants from other sources. They

include among others—Cocculus (4), Cleome (1), _Perrottetia_ (1),

Mezoneuron (1), _Lythrum_, _Sicyos_ (8), Peucedanum (2), Campylotheca

(12), Senecio (2), Lobelia (5), Embelia (1), _Chrysophyllum_ (1),

Rauwolfia (1), _Nama_ (1), Osmanthus (1), _Jacquemontia_ (1), Breweria

(1), Cuscuta (1), Lycium (1), _Sphacele_ (1), _Phytolacca_, Rumex (2),

_Urera_ (2), Pilea, Dracæna (1), Naias, Potamogeton. Those printed in

italics are regarded as derived from America; whilst the figures in

brackets indicate the number of endemic species, nearly all of the

genera except the five above indicated possessing only peculiar species,

and these five (Lythrum, Phytolacca, Pilea, Naias, Potamogeton) are only

represented by species found outside the group.

American genera form a more conspicuous element than they do amongst the

genera that have been generally dispersed over the Pacific, those

exclusively American being fairly represented, making a third of the

whole. We find, for instance, in the Hawaiian “Olomea,” Perrottetia

sandwicensis, a small tree that represents in the woods of all the

islands the Perrottetias of Mexico and the Andes; whilst with some of

those genera that, like Sicyos and Urera, are at home in both the Old

and New Worlds, we obtain indications of America being the source of the

Hawaiian plants. A few genera again, like Lythrum and Phytolacca, are

represented in Hawaii by American species.

Plants with drupes, berries, or other fleshy fruits likely to attract

frugivorous birds compose about a third of the total number of these

residual genera, whilst fruits or seeds, that were in all probability

originally brought entangled in a bird’s feathers, are represented by

Sicyos. Some of the genera with stone fruits, such as Osmanthus, to

which belongs the Hawaiian Olive, present special difficulties on

account of the size of the stone, in this case two-thirds of an inch in

length. There are also a number of genera with large dry fruits and

sometimes large seeds, of which the method of dispersal is not easy to

discover. Thus, Mezoneuron, a Leguminous genus with seeds an inch across

(2·5 cm.), and Peucedanum, of the Umbelliferæ, with mericarps half to

three-quarters of an inch (1·2 to 1·8 cm.) in length, offer serious

difficulties to the student of plant-dispersal. In discussing the

difficulty connected with Mezoneuron (see Chapter XV.) he will keep in

view the possibility that the original species may have been a littoral

plant possessing seeds dispersed by the currents, seeds that lost their

buoyancy when the plant established itself inland, just as is now taking

place with Afzelia bijuga, a Leguminous littoral tree of Fiji (see

Chapter XVII.).

He will also find much to puzzle him in the mode of dispersal of the

Hawaiian residual genera of the Convolvulaceæ (Breweria, Jacquemontia,

and Cuscuta) that possess only endemic species, and he will speculate as

to the manner in which seeds that would seem to possess but little

attraction for birds and have no capacity for transportation by the

currents could ever have reached these islands, and he will ask himself

why it is that the agencies of dispersal, whatever they are, have now

ceased to be active. He will perhaps see a way out of his difficulties

when he perceives that if isolation has led to the development of

peculiar species in Hawaii, it has strangely enough in the case of the

Myrsinaceous genus Embelia produced the same effect over the whole range

of the genus, and that Hawaii has in this respect derived no advantage

from being an oceanic group. According to Carl Mez, nearly all the

ninety species of this Old World genus are restricted in their areas,

whether continental or insular (“Myrsinaceæ,” _Das Pflanzenreich_,

1902); and indeed we do not seem justified in assuming that the

isolating influences in the case of this genus have been more effective

in Hawaii in the mid-Pacific, or in Mauritius in the Indian Ocean, than

they have been in continental regions like the Deccan and Nyassa Land,

in all of which localities endemic species occur.

The remarkable development of the Cucurbitaceous genus Sicyos, in Hawaii

alone of all the tropical Pacific groups, will attract his attention,

and he will find here another instance of that predominant principle in

the distribution of Pacific plants, where in a widely-ranging genus we

find one of its species covering most of its area, whilst the other

species are more or less localised. He will wonder at the limitation to

Hawaii of a genus like Dracæna, that is so well adapted for dispersal

over the Pacific by frugivorous birds; and in endeavouring to explain

the presence in the Hawaiian forests of the gigantic Rumex, R.

giganteus, he will remember that the small group of Tristan da Cunha,

equally isolated in the South Atlantic, possesses an endemic species of

the same genus. He will discover in the recognised dispersing agencies

of wild ducks and other waterfowl an explanation of the occurrence in

Hawaii of the aquatic genera Naias and Potamogeton; but he will be

puzzled at their restriction to this group alone of the three tropical

Pacific archipelagoes here especially discussed.

Amidst these various perplexities he will probably look with relief on

the appearance of Phytolacca brachystachys, an endemic species of the

American “pokeweeds”; and he will feel grateful to the American

botanists like Professor Weed when they tell him that in the United

States crows, blackbirds, and other birds successfully disperse these

plants, the seeds of which are sometimes able to pass through the

alimentary canal undigested.

But by far the most significant lesson that the student of distribution

will carry away from his study of the Hawaiian residual genera will be

that which he learns from the genera Embelia and Naias. He perceives

here that not only with a typical land-genus has specific

differentiation occurred to much the same extent in the continental and

insular localities of its range, but that even with a typical genus of

submerged aquatic plants, where the conditions of existence are as

uniform as they are varied in the case of land plants, the process of

differentiation has proceeded on the same broad lines in the interior of

a continent and in an island in mid-ocean.

The following notes on some of the residual genera refer more

particularly to matters connected with distribution and dispersal.

_Osmanthus_ (Oleaceæ).—This genus, according to the _Index Kewensis_,

contains six species localised in their several habitats of North

America, Hawaii, Japan (two), Hongkong, and the Himalayas. Its

representative in this group is the Hawaiian Olive, the Olea

sandwicensis of Gray, a prevailing tree in the lower and middle woods

(1,000 to 4,000 feet) of all the islands, which, like other Hawaiian

plants, such as those of the genera Eurya and Antidesma, indicates that

the group has been sometimes independently stocked from the regions of

the northern hemisphere. The drupe of this tree contains a stone

two-thirds of an inch (17 mm.) in length, and suitable for dispersal by

frugivorous birds; and birds have evidently distributed the tree all

over the group. In fact Mr. Perkins in mentioning the favourite food of

birds of the Hawaiian genus, Phaeornis, refers to the fruits of this

tree as well as of the Opiko (Straussia) and of the Olapa

(Cheirodendron). When, however, we come to consider the feasibility of

the stones of the genus having been thus originally carried to Hawaii

either from Japan or from North America, we meet with the difficulty

presented to us by other Hawaiian genera with stone-fruits, such as

Elæocarpus, or with berries containing large seeds, such as Sideroxylon.

_Sicyos_ (Cucurbitaceæ).—This genus comprises about thirty-five known

species, of which three-fourths are confined to the New World, being

mainly South American, whilst the remainder are restricted to Hawaii,

with the exception of two species in the Galapagos Group and Norfolk

Island, and a widely-ranging species, S. angulatus. The plant just

named, the small fruits of which possess hooked spines, adapting them

for dispersal in a bird’s plumage, occurs in Africa, Australia, New

Zealand, and America, but has only been recorded in the Pacific islands

from the Kermadec Group.

North America was probably the home of the original Hawaiian species.

Hillebrand describes eight species, of which five are not found in more

than one island, whilst one species is spread over most of the islands.

The fruits vary much in size, and only in a couple of species do they

now possess any fitness for attaching themselves to plumage, some of

them being pubescent or even glabrate, so that deterioration in the

capacity for dispersal has here taken place. Their size is usually a

quarter to half an inch (6-12 mm.); but it is noteworthy that the

species with the largest fruit (Sicyos cucumerinus, one to two inches,

or 25 to 50 mm.) is the species most widely dispersed over the group.

This appears to indicate that there is some other means of inter-island

dispersal in this archipelago than by attachment to birds’ plumage. The

isolation of the genus in Hawaii from the rest of the world is, however,

complete, since all the species are endemic; and when, therefore, we

come to ask how Sicyos angulatus, that has been dispersed in the recent

era over America, Australia, and New Zealand, is not found in these

islands, we are brought face to face with the ever-recurring difficulty,

the suspension in later times of the agency of dispersal in the tropical

North Pacific.

_Jacquemontia_ (Convolvulaceæ).—This genus, which is chiefly American,

is represented in Hawaii by a peculiar species, J. sandwicensis. This

species grows occasionally on the sandy beaches associated with

Heliotropium anomalum and Tribulus cistoides; but it is most at home on

rocky ground and on old lava-flows near the sea-border, making its abode

often in the pockets of black sand produced by the disintegration of the

lava. Its small seeds sink in sea-water even after prolonged drying; and

it can perhaps be supposed that the original seeds were brought from

North America in the crevices of a drifting log. According to Ridley,

Fernando Noronha possesses a peculiar species also growing near the sea;

and it may be that the drifting log has here been the agent also: but in

neither case would this explanation account for the endemic character of

the species.

_Cuscuta_ (Convolvulaceæ).—It would seem that with the exception of

Hawaii, where an endemic species, C. sandwichiana, occurs, no other

oceanic group in the globe possesses a peculiar species of the Dodders.

With the exception of an endemic species in New Zealand, and an

introduced species in Fiji which is found usually near the gardens of

the white residents on Viti Levu, the genus takes but little part in the

Pacific floras. The Hawaiian species is a characteristic beach-plant

growing on Ipomœa pes capræ, Scævola Kœnigii, Tribulus cistoides, and on

other plants that find a permanent or a temporary abode on the beaches.

We learn from Ridley and Moseley that Cuscuta americana in Fernando

Noronha finds its host also in Ipomœa pes capræ. Since the seeds of the

Hawaiian plant and of the introduced Fijian species possess no buoyancy,

even after drying for years, we cannot look to the agency of the current

unless we call the drifting log to our assistance, and in that case the

endemic character of the Hawaiian species would present the difficulty

already alluded to in the case of Jacquemontia. The seeds of the

Hawaiian plant are about one-twelfth of an inch (2 mm.) in diameter, and

as far as size is concerned they might have been transported in a bird’s

stomach; but, on account of the rapidity with which the seeds of the

genus absorb moisture and swell up, it is most unlikely that they would

escape injury. This is one of the several difficulties in

plant-dispersal which New Zealand and Hawaii share in common. Further

remarks on the germination of the Hawaiian species are made in Note 69.

_Rumex_ (Polygonaceæ).—Hawaii possesses two peculiar species of Rumex, a

genus not recorded from any other of the Polynesian groups. One of these

species, R. giganteus, is a very remarkable plant, growing to a height

of thirty or forty feet when supported by trees. It is noteworthy that

the small group of Tristan da Cunha in the South Atlantic possesses a

species, R. frutescens, confined to those islands (_Bot. Chall. Exped._,

ii. 154). Both Hawaii and Tristan da Cunha lie in mid-ocean, cut off

from the nearest continent by some 1,800 or 2,000 miles of sea; and we

may have to choose between the bird and the current in selecting the

agency concerned with the transportation of the original seeds; or

perhaps they have co-operated. Birds could disperse the nutlets of Rumex

as readily as they do those of Polygonum, and I have found these fruits

at times in the stomachs of partridges. On the other hand, Rumex fruits

occur amongst the drift stranded on beaches in England and in

Scandinavia; and, as indicated by the observations of Sernander and

myself in these two localities, they float through the winter in ponds

and rivers, germinating afloat in the spring. The nutlets sink, but they

owe their buoyancy to the persistent perianth. In my sea-water

experiments the fruits of Rumex hydrolapathum and R. conglomeratum were

still afloat after from six to twelve months’ immersion, and their seeds

subsequently germinated. It is quite possible, therefore, that currents

can carry these fruits unharmed to oceanic island-groups like Hawaii and

Tristan da Cunha.

_Dracæna_ (Liliaceæ).—This Old World genus, which on account of its

berries is eminently suited for dispersal by frugivorous birds, is

represented in Polynesia by a solitary species (D. aurea) peculiar to

the Hawaiian Group. Attaining a height of twenty to twenty-five feet, it

often forms a striking feature in the vegetation of the open wooded

regions up to altitudes of 3,000 feet. I found it growing in abundance

in the large island of Hawaii between Waimanu and Waipio, and on the

northern slopes of Hualalai. It grows in a variety of stations, and I

came upon it once in the broken-down caverns of an old lava-flow that

were frequented by pigeons which no doubt brought the seeds. Its

conspicuous yellow berries have hard rounded seeds a quarter of an inch

(6 mm.) across and weighing two to three grains when dry, which would

probably withstand injury in a bird’s stomach, the minute embryo being

protected by a very tough albumen. Neither the entire berry nor the seed

could be transported by currents, the last sinking even after drying for

six years.

_Naias_ (Naiadaceæ).—If we except New Caledonia, where two or three

species have been found, Hawaii is the only island-group in the tropical

Pacific from which this interesting world-ranging genus of submerged

aquatic plants has been recorded. Chamisso, the celebrated naturalist of

Kotzebue’s expedition, collected Naias marina in Oahu in the early part

of last century; but apparently it did not come under Hillebrand’s

observation in the group. However, in 1897 I found it in another

locality, namely, just within the mouth of the Waipio, a river on the

north-west side of the island of Hawaii. The mature fruits of this genus

have never been experimented on by me; but there is nothing in the

structure of the fruits to indicate that they have any buoyancy, or to

show that they differ in this respect from the fruits of other

completely submerged aquatic plants like Ceratophyllum, Ruppia, and some

of the Potamogetons. It is to ducks and other waterfowl that we must

attribute the dispersal of this and the other genera just mentioned over

wide tracts of ocean, a subject dealt with in discussing those plants.

The Hawaiian Group probably represents the most isolated locality

occupied by this genus, since none of the other islands from which

species have been recorded, such as New Caledonia, Mauritius, and

Bourbon, are so far removed from continental regions. The source of the

Hawaiian form of Naias marina lies evidently on the Asiatic side of the

Pacific, since it is referred by Mr. Rendle to the variety

“angustifolia,” an Asiatic plant found also in the island of Bourbon and

in West Australia, but not recorded from the New World. The important

little monograph of the genus by Mr. Rendle (“Naiadaceæ,” in Engler’s

_Das Pflanzenreich_, 1901) is full of suggestiveness for the student of

plant-distribution. His interest is excited when he discovers that one

of the most typical genera of aquatic plants displays the same principle

of differentiation at work that is so well illustrated by many of the

land genera of the Pacific islands. I refer to the principle implied in

the existence of a widely-ranging genus comprising “a polymorphic

species occurring over almost the whole area of the genus,” as well as a

number of less widely distributed species, most of which have

“restricted areas and fall for the most part into small geographical

groups.” I have just been quoting Mr. Rendle’s description of the

distribution of Naias, the “polymorphic” species concerned being N.

marina; but it need scarcely be remarked that it would apply just as

well to several of the land genera dealt with in the previous chapter

(XXVI.), such as Alphitonia, Metrosideros, Pisonia, &c.

Although there is such a contrast in the degree of uniformity of their

life-conditions between land and water plants, a strictly aquatic plant

being but slightly affected by changes in the physical conditions that

are accompanied by a complete transformation in the character of the

terrestrial vegetation, yet—and this is the important point—we find the

same principle of differentiation at work with both land and water

plants. If one wished to produce proof of the contention that the

production of new species is largely independent of external conditions,

one could not do better than take the cases of Elæocarpus, Metrosideros,

and Naias. In all cases we see a widely-ranging polymorphous species

settling down and “differentiating” in particular localities or regions,

and forming subcentres for the distribution of the genus.

_Potamogeton_ (Potameæ).—Though well suited for dispersal by waterfowl,

the Potamogetons have been recorded from the Hawaiian and Marianne

Islands alone among the tropical groups of the open Pacific. The genus,

though not so well represented in insular floras as we might have

expected, is still not infrequently to be found. Widely-ranging species

have been observed in the Azores, Madeira, and the Canaries in the

Atlantic, as well as in Hawaii in the Pacific; whilst species have been

recorded that are peculiar to Martinique, the Mascarene Islands, and to

the Marianne Group. Hillebrand gives for Hawaii, Potamogeton fluitans, a

plant of the Old and New Worlds, and P. pauciflorus, a North American

species; whilst in the _Index Kewensis_ a peculiar species, P.

owaihiensis of Chamisso (which is, however, regarded by Hillebrand as a

form of P. fluitans), is also accredited to the group. Owing, however,

to the paucity of streams and rivers this genus takes no prominent part

in the Hawaiian flora, and the species seem to have been recorded alone

from Oahu. As they were discovered by Chamisso in the early part of last

century they are in all probability truly indigenous in Hawaii, even if

none are peculiar to the group.

That ducks and similar birds are the agents in carrying the seeds of

Potamogeton to oceanic islands cannot be doubted. About twelve years ago

I examined the stomachs and intestines of thirteen wild ducks obtained

in the London market. Three of them contained in all forty-one

Potamogeton seeds, or rather “stones,” most of which subsequently

germinated in water. In one of my experiments, carried out in the month

of December, I fed a domestic duck with the fruits of Potamogeton

natans. They appeared in quantity in the droppings, for the most part

divested of their soft coverings, but otherwise uninjured. Sixty per

cent. germinated in the following spring; whilst of those left in the

vessel, from which the duck had been fed, only one per cent. germinated

in the next spring, and another year elapsed before any number did so.

These results were published in _Science Gossip_ for September, 1894.

One often reads in books of travel interesting remarks bearing

indirectly on the dispersal of the Potamogetons. Thus, when Sir Joseph

Hooker (then Dr. Hooker) noted in his _Himalayan Journals_ the

occurrence of P. natans in the Neongong Lake in the Himalayas, and the

presence of coots, he most probably mentioned the bird that brought the

plants, coots being active distributors of the seeds of water plants. It

is of importance to remember that (as shown in my experiment on the

duck) seeds of water-plants are voided in a condition peculiarly

favourable to early germination. Ducks, coots, and other water birds

might often be characterised as “travelling germinators.” My experiment

showed that seven to eight hours at least were occupied by Potamogeton

nutlets in passing through the digestive canal of a duck, and that

probably nine or ten hours would be required after an average full meal.

But this does not represent the possible maximum period, since the bared

“stone” may remain in the gizzard for a long time with ordinary gravel.

Most of the Potamogeton fruits found by me in wild ducks were obtained

from the gizzard, where they were mixed with gravel and other hard seeds

or seedvessels, as described in Chapter XXXIII. Such fruits afterwards

germinated. With regard to the chances, therefore, of the fruits of

Potamogeton being carried by a bird without injury across an ocean, we

may infer that, whether they are retained in its body for only ten hours

or for as long as three or four days, they will preserve in some cases

their germinating power.

HAWAIIAN GENERA FOUND IN TAHITI TO THE EXCLUSION OF FIJI.

Taking only the genera that are strictly indigenous, and excluding

therefore all those introduced by the aborigines, the number available

for establishing an independent connection between the Hawaiian and

Tahitian regions is exceedingly few. Amongst the Hawaiian shore-plants

not found in Fiji proper but occurring in the Tahitian region are

Heliotropium anomalum and Sesuvium portulacastrum. The last-named,

however, has been recorded from Tonga, which lies within the Fijian

area; whilst the first will probably be found in the same region.

Amongst the Hawaiian and Tahitian mountain genera not recorded from Fiji

proper are Nertera, Vaccinium, Cyathodes, and Luzula. As is pointed out

in Chapter XXIII., the absence of these genera from Fiji is connected

with the relatively low elevation of those islands, though it is quite

possible that one or more of them may yet be found on the highest

summits of Fiji; and indeed Nertera depressa and Vaccinium have been

discovered in the more elevated uplands of Savaii in Samoa.

After removing the littoral plants and the mountain genera, there are

probably not more than half a dozen inland genera that connect the

Hawaiian lowlands with the Tahitian region to the exclusion of the

Fijian Group; and Byronia (Ilicineæ), Reynoldsia or Trevesia

(Araliaceæ), Phyllostegia (Labiatæ), and Pseudomorus (Urticaceæ) may be

taken as examples. Of these, Pseudomorus, which has a small drupaceous

fruit suitable for dispersal by frugivorous birds, has been recorded

from New Caledonia, and not improbably it exists in the Fijian area; and

the same may be postulated of Reynoldsia, which is discussed in a later

page, since it has been found in Samoa. We may almost form the same

opinion of Byronia, since it exists in Australia. This genus of small

trees contains only three known species, one in Australia, one in

Tahiti, and one in Hawaii. Its fleshy drupes, about a third of an inch

(8 mm.) in size, would attract birds, and their numerous cartilaginous

pyrenes would probably pass unharmed through a bird’s alimentary canal.

Phyllostegia, a Labiate genus with fleshy nucules that might attract

birds, is, with the exception of a solitary Tahitian species, entirely

confined to Hawaii (see Chapter XXII.).

From these data it may be inferred that the interchange of plants

between the regions of Hawaii and Tahiti to the exclusion of Fiji has

been very slight. The facts of distribution are just such as we might

look for in the case of a general dispersal over the oceanic groups of

the tropical Pacific, with the altitudes of the islands playing a

determining part. In this general dispersal Hawaii has shared; and

except in the case of Phyllostegia it is evident that this group has

kept nearly all it received and has distributed but little.

HAWAIIAN GENERA FOUND IN FIJI TO THE EXCLUSION OF TAHITI.

We shall be able to throw further light on the floral history of Hawaii

by discussing the few tropical genera, not a score in all, that it

possesses in common with Fiji to the exclusion of the Tahitian region.

The following genera offer themselves for treatment:—Eurya

(Ternstrœmiaceæ), Gouania (Rhamnaceæ), Maba (Ebenaceæ), Sideroxylon

(Sapotaceæ), Antidesma (Euphorbiaceæ), Pleiosmilax (Smilaceæ), and

Ruppia (Potameæ).

These seven genera, which with the exception of Ruppia, an aquatic

genus, are only represented in Hawaii by peculiar species, possess in

all cases, except Gouania and the last-named genus, drupaceous or

baccate fruits likely to attract frugivorous birds. Two of them, Eurya

and Antidesma, have their home in Malaya and in the Asiatic continent;

three of them, Gouania, Maba, and Sideroxylon, are found on both the

Asiatic and the American sides of the Pacific Ocean; whilst Pleiosmilax

should, strictly speaking, be regarded as a Polynesian subgenus of

Smilax, a world-ranging genus; and Ruppia is a cosmopolitan brackish-

and salt-water genus.

It is highly probable that Fiji received almost all these genera from

the Old World through Malaya; and in some cases the resemblance between

the Malayan and the Fijian species is so close that, as in Gouania, Dr.

Seemann questioned if they were not forms of the same species. In other

instances, as with Maba, we find a widely-ranging Asiatic and Malayan

species, like Maba buxifolia, extending into Western Polynesia, where it

is accompanied by other species peculiar to that region. But if the

genera were able subsequently to extend their range thence to Hawaii, it

is difficult to understand why they have not reached the Tahitian

region. It is therefore likely that Hawaii received most of these genera

by a northern route and not through the South Pacific; and it is

legitimate to suppose that when Old World genera like Eurya and

Antidesma occur in north-eastern Asia, as in Japan and in the

neighbouring mainland, Hawaii received the genus by that route. In the

case of Eurya it is noteworthy that Fijian and Samoan forms, regarded by

Seemann and Gray as distinct species, are viewed by Reinecke as forms of

E. japonica, an extremely variable species found in Japan. With genera

like Gouania and Maba, that exist on both sides of the Pacific, it is

possible that they may have originally reached Hawaii from America.

A noticeable feature in the instance of genera like Maba and Sideroxylon

is that hard seeds or pyrenes 3/4 to 1 inch (18 to 25 mm.) in length

have seemingly been transported by frugivorous birds across the ocean to

Hawaii. This at first sight seems improbable; but it is known that

fruit-pigeons can swallow very large drupes, as in the case of those of

Canarium, Dracontomelon, and Elæocarpus, afterwards disgorging the

“stones.” They have carried such stones to Fiji, across some 500 or 600

miles of ocean; and unless we impute a continental origin to Hawaii we

must assume that in some cases, as with Elæocarpus, Maba, and

Sideroxylon, they have been able to transport these large stones or

pyrenes to that group. The extent of ocean to be crossed is no doubt

much greater, but this area of the Pacific is not without some small

half-way groups that would serve as resting-places.

That fruits of the order Sapotaceæ are much appreciated by fruit-pigeons

is already known. We learn from Kirk that the fruits of Sideroxylon

costatum (Sapota costata) are a favourite food of the New Zealand

fruit-pigeon, the fruits, about an inch long, containing three hard

crescentic bony seeds nearly as long as the fruit. The natives of Vanua

Levu informed me that a Fijian species of Sideroxylon with hard seeds

about an inch long was much appreciated on account of its fruit by the

pigeons. I found the hard, sound seeds of a species of Sapota,

two-thirds of an inch (or 16 mm.) in size, in the crop of a Fijian

fruit-pigeon. The similarly large seeds of a species of Achras were

identified by Mr. Charles Moore, of Sydney, amongst a collection of

seeds, &c., found by me in the crops of fruit-pigeons shot in the

Solomon Islands (Guppy’s _Solomon Islands_, p. 293). It may be added

that the difficulty concerned with Sideroxylon in Hawaii is the

difficulty concerned with other large-seeded Sapotaceous trees in Fiji

and New Zealand, and the same explanation must be applied to all. Some

further remarks on the Sapotaceæ in the Pacific are given below.

The mode of dispersal of some of these genera is illustrated in other

regions. The berries of Pleiosmilax, a subgenus of Smilax, are well

suited for aiding the dispersal of the genus by frugivorous birds; and

we learn from Prof. Barrows (Weed, p. 42) that in the United States

crows feed on the fruits of Smilax rotundifolia and disperse the seeds.

On the other hand, it is not at first sight easy to understand how a

genus like Gouania has been distributed over the tropics of the globe,

since it possesses dry capsular fruits about half an inch across,

separating into three woody cocci that appear most unlikely to attract

birds. The same difficulty exists, however, with other dry-fruited

widely-ranging genera like Alphitonia and with many of the Euphorbiaceæ.

Amongst these genera found in Hawaii and Fiji to the exclusion of Tahiti

we can at times detect indications of the operations of a polymorphous

species as described in Chapter XXVI., when a widely-ranging highly

variable species is associated in some groups with peculiar species. We

see some evidence of this in the genera Gouania, Maba, and Eurya,

alluded to on a previous page. (See also _Bot. Chall. Exped._, iii. 134,

under “Gouania.”)

One of the mysteries of the Pacific is concerned with the distribution

of the Sapotaceæ, the dispersal of which by frugivorous birds has been

dealt with above. It is strange that whilst the order seems to have

found a _rendezvous_ in Tonga, no one except Horne appears to have

recorded any of the genera from Samoa. They are fairly well represented

in Fiji; but it is in Tonga that we especially note the gathering

together of several Sapotaceous trees with large heavy seeds, of the

genera Bassia, Mimusops, and Sideroxylon. Besides owning one or two

species of Sideroxylon in common with Fiji (Burkill), this small group

possesses Bassia amicorum and Mimusops kauki, both of which were found

there by Forster at the time of Cook’s visit. In a list of a small

collection of plants made by him in Upolu in the Samoan Group about

1879, Horne includes two species of Sideroxylon (_Year in Fiji_, p.

286); and according to Seemann there is a Sapotaceous tree in Wallis

Island. A species of Bassia exists in Rarotonga, the seeds of which,

from Mr. Cheeseman’s description of the fruit, must be almost an inch

long. Drake del Castillo refers to an endemic Tahitian tree near

Mimusops; but its fruit was not known to him.

As already indicated, the difficulties connected with the Sapotaceæ

affect the whole Pacific from New Zealand north to Hawaii and from Fiji

east to Tahiti. We are driven to appeal to the agency of frugivorous

birds, at least in the case of Sideroxylon, since some fruits

experimented on by me in Fiji sank at once or in a day or two, the seeds

having no buoyancy. That birds actually disperse the seeds of this and

other genera of the order has been already pointed out, yet it is

possible that currents have at times aided in the dispersal of some of

the genera. This is indicated by the circumstance that, as we learn from

Schimper, some Sapotaceous trees are to be included in the Malayan

strand-flora, namely, Sideroxylon ferrugineum, Mimusops kauki, and M.

littoralis, all occurring as well on the Asiatic mainland, the first

growing also in the Liukiu Islands, and the last in the Andaman and

Nicobar Groups.

_Ruppia maritima_ (Potameæ).—This cosmopolitan aquatic plant has only

been recorded in Polynesia from Hawaii, Samoa, and Fiji. It had not been

collected in Fiji before my discovery of it in 1897. Amongst other

oceanic islands where it occurs may be mentioned the Bermudas, where,

according to Hemsley, it exists as an indigenous plant in the lagoons.

Chamisso first noticed it in Hawaii, and Hillebrand remarks that it

grows in shallow waters along the coasts. Amongst other localities where

I noticed it in this group may be mentioned the north-west coast of the

large island of Hawaii between Kailua and Keahole Point. Here in 1896 it

was thriving in brackish-water ponds, with Sesuvium portulacastrum

growing at the edges. Reinecke observes that it occurs in similar ponds

in Samoa. In 1897 I found it in abundance in the Rewa estuary (Fiji),

both in the creeks and in the main channel. In the following year it was

not to be found in this locality, a circumstance noticed both by the

natives and by resident whites. The fruits of this plant possess no

floating power, sinking, even after prolonged drying, in a few hours. It

is to ducks and to birds of similar habit that its dispersal must be

attributed.

THE ABSENTEES FROM HAWAII.

It has been before remarked that of the 330 or 340 genera of

flowering-plants recorded from Fiji some 200 are not known in Hawaii. It

will only be possible to deal with the absent genera in a cursory

manner; but enough will be done to show that we are face to face here

with a multitude of the seeming inconsistencies that so often beset the

study of plant-distribution.

A host of plants are unrepresented in Hawaii, of which it may be said

that their seeds or fruits are not less suited for being carried across

the Pacific than those of many that are now in that group. On the other

hand, a number of genera exist there which we should never expect to

have been endowed with the capacity, and to have received the

opportunity, of crossing nearly 2,000 miles of ocean. Yet perhaps when

Nature acts in a wholesale fashion and excludes entire orders we may be

able to perceive the dim outlines of a principle of exclusion at work.

But even here much caution and some clearing of the ground are needed.

For example, having regard to the several modes of dispersal possessed

by the great variety of fruits and seeds of the Sterculiaceæ, it would

be almost meaningless to remark that the order so well represented in

Fiji is practically non-existent in Hawaii as far as truly indigenous

plants are concerned. It is true that two species of Waltheria are here

present, but one of them W. americana, is a weed probably introduced by

the aborigines whilst the other, W. pyrolæfolia, recorded from a

solitary locality by the Wilkes Expedition, has seemingly never been

found since. From the standpoint of dispersal the genera Sterculia,

Heritiera, Kleinhovia, Melochia, and Commersonia, that are represented

in Fiji but not in Hawaii, cannot be discussed together. With Sterculia

is concerned the dispersal by birds of large seeds, an inch in length,

not particularly well protected, the genus being confined to Fiji alone

of all the oceanic Pacific groups. Heritiera is only represented by a

littoral species, the large fruits of which are carried great distances

by the currents; and no other agency of dispersal is here possible. The

last three genera are distributed over the South Pacific, their

relatively small seeds being probably in the main dispersed by

granivorous birds; whilst the setose fruits of Commersonia may have been

at times transported in birds’ plumage.

It is more legitimate, perhaps, to speak collectively of the orders

Meliaceæ and Melastomaceæ as absent from Hawaii; but even here the issue

raised is one concerned rather with opportunities than with capacities

for dispersal. Several years ago, M. Casimir de Candolle remarked that

“it is hardly credible that the Meliaceæ should be entirely absent from

the Sandwich archipelago” (_Trans. Linn. Soc. Bot._, vol. i. 1880). Yet

it can scarcely be said that this is a matter connected with means of

dispersal. Amongst the Meliaceous genera represented in Fiji, Vavæa and

Aglaia have a berry, Melia has a drupe, and Dysoxylum has a capsule. So

again with the Melastomaceæ; it possesses at least six genera in Fiji,

two in Tahiti, and none in Hawaii. Whilst the genera Melastoma and

Medinilla have baccate fruits with minute seeds, Astronia has a capsule

with similar seeds, and Memecylon has a single-seeded berry. Since,

however, minute seeds are most typical of the order, those of Melastoma

denticulatum being about one-fiftieth of an inch or ·5 mm. in size, it

would seem that this character has not aided its dispersal in the

Pacific so far as Hawaii is concerned. From the circumstance that

berries, drupes, and capsules are represented in these two Fijian orders

we may form the opinion that their non-occurrence in Hawaii is due not

so much to lack of capacities for dispersal as to failure of

opportunities.

This opinion is much strengthened when we come to deal with the

individual genera, where the predominant cause of the absence of so many

Fijian genera from Hawaii is concerned with the failure of the agencies

of dispersal. It is not a question of a difference in size between the

groups, since, although the surface-area is approximately the same in

both groups, Hawaii possesses only two-thirds of the number of genera

occurring in Fiji. It is not a question of capacity for dispersal across

an ocean, since birds have transported across the Pacific to Hawaii the

“stones” and large seeds of genera like Elæocarpus and Sideroxylon, a

feat that would have been deemed impossible by many botanists. It is no

lack of capacity for dispersal that has excluded Loranthus from Hawaii

and has admitted Viscum.

Few genera, indeed, would seem to be better fitted for dispersal by

frugivorous birds in the Pacific than that of Ficus. Its fruits are

known to be eaten by birds all over the area of the genus; and we find

the species distributed over the South Pacific from Fiji to Tahiti, but

they are quite absent from Hawaii. This is the more remarkable on

account of the occurrence of a species of Ficus resembling a banyan in

Fanning Island about 900 miles south of the group (_Bot. Chall. Exped._,

iii. 116, 194), and because the Hawaiian Islands possess the Meliphagidæ

or Honey-eaters, which are widely distributed in Polynesia and are known

to feed on these fruits—a matter further discussed in my treatment of

Ficus later on in this chapter.

Of several Rubiaceous genera with fleshy fruits that are represented

both in Fiji and Tahiti, such as Stylocoryne and others, and of those

Rubiaceous genera with minute seeds that, like Ophiorrhiza, are

distributed over the South Pacific, none occur in Hawaii. Here we find

represented other genera of the order, like Gardenia, Plectronia, and

Coprosma, that do not appear to be better fitted for dispersal by

frugivorous birds than many of the genera not existing there. If birds

have carried to Hawaii in their plumage the fruits of Pisonia and

Sicyos, it cannot be merely a question of capacity for dispersal that is

concerned with the restriction to the South Pacific of genera with hairy

seeds, such as Trichospermum, Alstonia, and Hoya.

It is unnecessary to dwell longer here on the subject of the Hawaiian

absentee-genera, since many of the absent plants will be discussed when

dealing with the peculiarities of the Fijian flora. The data there given

all go to show that mere lack of capacity for dispersal over the Pacific

often counts for little in supplying us with an explanation of the

absence of so many likely genera from the Hawaiian flora. Hawaii has

only been stocked with those genera common to Fiji and Tahiti that could

have reached it during each age of general dispersal over the Pacific.

In later eras the dispersing agencies have been mainly active in the

tropical South Pacific; and thus it is that, as will be pointed out in a

later page, the bulk of the plants of the Malayan era are confined to

the region between Fiji and Tahiti. In a still later period the

dispersing agencies have confined their operations mainly to Western

Polynesia and the last immigrant genera have not reached beyond the

Fijian region.

The whole story of plant-life in the tropical Pacific is bound up with

these successive stages of decreasing activity of the dispersing

agencies. The story of plant-distribution in this region is well

illustrated in its earlier phases of general dispersion in the floral

history of Hawaii, in its later phase by those Asiatic genera that have

only crossed the South Pacific to Tahiti, and in its last phase by those

genera that have never extended beyond the groups of the Fijian area.

The area of active dispersion, that first comprised the whole of the

tropical Pacific, was afterwards restricted to the South Pacific, and

finally to the western portion of that area. It can scarcely be doubted

that these successive stages in the contraction of the area of active

dispersion of plants in the Pacific were accompanied by a corresponding

diminution in the general distribution of birds in the same ocean, to

which it stood in the relation of an effect to a cause.

TAHITI.

The peculiarities of the Tahitian flora as compared with Hawaii and Fiji

may be discussed by treating first those genera that are alone

represented in Tahiti, the “residual” genera; then those that it

possesses in common first with Hawaii and then with Fiji; and lastly by

pointing out the more noticeable gaps in the flora. By Tahiti is

typically signified the whole Tahitian region, which includes the

Austral and Cook Groups, the Society Islands, the Paumotus, and the

Marquesas.

THE TAHITIAN RESIDUAL GENERA.

The non-endemic genera occurring alone in the Tahitian region and not

found either in Hawaii or in one or other of the three groups of the

Fijian region (Fiji, Tonga, Samoa) are not more than half a dozen. These

six genera are exceedingly interesting; but since each tells a different

story and gives its own independent indication they cannot be treated in

a collective sense. Nor are they all to be regarded as anomalies in

plant-distribution, since with a single exception there is scarcely one

concerning which it is not in some way possible to give an explanation

of its isolation without coming into conflict with the principles of

plant-dispersal. The exception is Lepinia tahitensis, which, without

presenting any very evident capacity for dispersal, has not been

recorded from any other localities in the Pacific than the far-separated

Solomon and Tahitian Groups. There is a suspicion that, as in the case

of the residual genera of Hawaii, America may have contributed some of

the original plants, since three of the genera, Buttneria, Coriaria, and

Bidens, occur in that continent, and in the case of Coriaria Tahiti

possesses a species found in South America as well as in New Zealand.

One of the trees in question is Cratæva religiosa, an Asiatic species,

which may be placed among a group of trees, including Cananga odorata

and Fagræa Berteriana, which, whilst they are much esteemed by the

inhabitants of the South Pacific for their fruits or their flowers, and

are often planted in and around their villages, possess fruits that

attract birds, and in the case of Cananga are known to be dispersed by

fruit-pigeons. Probably the aborigines and the birds have worked

together in the distribution of these trees.

The genera Buttneria of the Sterculiaceæ and Berrya of the Tiliaceæ are

represented in this region by species that must owe their dispersal to

birds, though I have no data relating to the matter of their dispersal,

their fruits being capsular, in the first case prickly. Coriaria is a

mountain genus in Tahiti and will be found discussed in Chapter XXIV. in

connection with the Tahitian mountain-flora. Its absence from the West

Polynesian groups is no doubt to be connected with their insufficient

altitude. In addition to the introduced Bidens pilosa, a common tropical

weed, Tahiti possesses two other truly indigenous species of Bidens, of

which one at least is peculiar to the region. The achenes of this genus

are well known to be adapted for dispersal in a bird’s feathers; and

since the genus has its principal home in America, no other indigenous

species having been recorded from South Polynesia, it is not unlikely

that the parent species was American.

One of the numerous enigmas of the Pacific floras is concerned with the

presence in the islands of Tahiti and Moorea (Eimeo), in the Society

Group, of the Apocynaceous tree, Lepinia tahitensis. The genus contains

this solitary species, which has been collected only in one other

locality, namely, in the Solomon Group, where it was obtained by the

Rev. R. B. Comins. Such an instance of disconnected distribution is rare

in the Pacific Islands, and undoubtedly it represents one of the

difficulties of the Tahitian flora. The fruits, which are indehiscent

and five or six inches in length, possess a fibrous pericarp and a

single seed. No data are to hand relating to the capacities for

dispersal possessed by this plant, but it is certain that it has had

some means of crossing the sea between the adjacent islands of Tahiti

and Moorea. (See Hemsley, _Journ. Linn. Soc. Bot._, xxx. 165.)

TAHITIAN GENERA FOUND IN HAWAII TO THE EXCLUSION OF FIJI.

This subject has been already discussed in this chapter in dealing with

the genera restricted to Hawaii and Tahiti.

TAHITIAN GENERA FOUND IN FIJI TO THE EXCLUSION OF HAWAII.

Excluding the orchids, sedges, and grasses, as well as the few endemic

genera, between sixty and seventy genera, or rather less than half of

the genera of the flowering-plants of Tahiti, are found in Fiji to the

exclusion of Hawaii. Of these, rather over a half are Old World genera;

about a third occur in both the Old and the New World; four are confined

to Polynesia, and not one is exclusively American. One-third are genera

now possessing in the Tahitian region endemic species either entirely or

in part, and in such cases we may consider that the agencies of

dispersal are now inactive or partially suspended; the others belong

entirely to the present era of dispersal. About half have more or less

fleshy fruits fitted for dispersal by frugivorous birds. About a fourth

have capsular or other dry fruits that must have been also dispersed by

birds preferring a drier diet. Three only possess hairy seeds or fruits

suitable for being carried in a bird’s plumage, namely, Commersonia,

Weinmannia, and Alstonia. There remain about a fourth of the total that

are shore-plants dispersed by the currents, being in two cases (Ximenia

and Kleinhovia) assisted by birds; whilst Triumfetta, another littoral

genus, is probably distributed by birds alone.

There are no cases of special difficulty from the standpoint of

dispersal in these sixty and odd non-endemic genera that Tahiti

possesses in common with Fiji to the exclusion of Hawaii. The lack of

difficulties connected with the dispersal of all these Tahitian genera

is worthy of note, because there are very few difficult genera amongst

the rest of the Tahitian flora. Excluding Lepinia tahitensis, which has

been already referred to, there are scarcely any “impossible” plants in

the Tahitian region; and even in this case, when the modes of dispersal

of Lepinia come to be investigated, it is likely that much of the

difficulty will disappear. Hawaii, as we have before seen, abounds with

perplexing questions of this nature. When dealing with the absentee

Tahitian genera, later on in this chapter, it will be shown that “size”

has played a prominent determining part in the exclusion of genera from

Tahiti, genera with seeds or “stones” exceeding half an inch or twelve

millimetres in dimension being, as a rule, unrepresented amongst the

truly indigenous plants.

My further remarks on these Tahitian genera found in Fiji but not in

Hawaii will be limited to some general observations from the standpoint

of dispersal. I will first discuss some of those genera that possess

only peculiar species. They belong to an era of dispersal that, as far

as Tahiti is concerned, is passing or has passed away. Here we have the

species of each genus more or less localised in the various South

Pacific archipelagoes; but, as with Meryta, Alstonia, and Loranthus, it

is often apparent that, although the Tahitian region is mainly outside

the zone of present dispersal, the different groups of the Western

Pacific are kept in touch by the possession of species in common. This

testifies to the activity of dispersal in that region after it had

become suspended in Eastern Polynesia. The connection between the

isolated endemic species of Eastern Polynesia and a species ranging over

the Western Pacific can sometimes be shown, as in the case of Loranthus,

where a species confined to the Society Islands and to the Marquesas is

very closely related to L. insularum, a widely-ranging West Polynesian

species that reaches eastward as far as Rarotonga.

We next have those genera like Grewia, Nelitris, Melastoma, Randia,

Geniostoma, Tabernæmontana, Fagræa, Bischoffia, Macaranga, and Ficus,

that possess in Polynesia one or more widely-ranging species. The agency

of the polymorphous species, which I have described in the preceding

chapter in connection with the general dispersal of Malayan plants over

the whole of Polynesia, is evidently also active when the work of

dispersal is restricted to the South Pacific. Its operation is to be

distinctly traced in all the genera above named except in Fagræa and

Ficus. Thus, in the genera Grewia, Melastoma, Randia, Geniostoma, and

Macaranga we find a single variable species ranging over the South

Pacific from Fiji to Tahiti, keeping all the groups in touch, but

associated in each, as a rule, with one or more peculiar species. A yet

earlier stage in the process is to be seen in those genera which, like

Nelitris, Tabernæmontana, and Bischoffia, possess only a solitary

species ranging over the South Pacific, varying in each group, but not

usually associated with endemic species. As with Melastoma, Macaranga,

and others, we can often trace the widely-ranging species of Polynesia

back to its home in Malaya, and with these and other genera the

connection between a species confined to a group and a variable species

ranging through all the archipelagoes of the South Pacific can sometimes

be detected in the affinity of their characters.

It is thus seen that one of the principal determining causes of the

differentiation of species in Polynesia lies in the failure of the

dispersing agencies, a widely-ranging species becoming in consequence

gradually isolated in the various groups. With some genera, as with

Ophiorrhiza, it is possible to show that the resulting endemic species

pass into each other by intermediate forms.

My further remarks on the Tahitian genera occurring in Fiji but not in

Hawaii will be devoted mainly to those with which I was most familiar

from the standpoint of dispersal.

The Tiliaceous genus GREWIA offers a good example of those Polynesian

genera which possess in the South Pacific a single widely-ranging

species associated often with endemic species in the individual groups.

It is likely that a polymorphous form, including most of the Polynesian

species, could be here constituted. The fruits are dryish drupes,

becoming black and moist when over-ripe, and containing three or four

pyrenes suitable for distribution by birds and five or six millimetres

in size.

The berries of NELITRIS, a genus of the Myrtaceæ, contain a few hard

seeds that are well fitted for dispersal by frugivorous birds. I am

inclined to follow Drake del Castillo, who considers that there is only

one varying species, N. vitiensis (Gray), which is distributed over the

whole of the South Pacific from the Solomon Islands to Tahiti. The

tendency of this widely-ranging species to vary in different groups is

indicated in the fact that some botanists have distinguished other

species within these limits. It is noteworthy that N. paniculata in

Indo-Malaya and N. vitiensis in the Pacific cover the whole range of the

genus. It would be interesting to establish a connection between them.

MELASTOMA, an Old World genus of forty and more species, has one very

variable species, M. denticulatum, which, as defined by Bentham, has the

range of the genus from tropical Asia across the Pacific to Tahiti. This

plant is associated in some groups, as in Fiji, Tonga, and Samoa, with

other more or less localised species, and it affords a good example of

the principle of polymorphism in species-making. The berry-like fruits

contain an abundance of minute seeds, half a millimetre in size, which,

when rendered adhesive by adherent pulp, might readily stick to

feathers, or they might pass unharmed through the alimentary canal of a

bird. It is noteworthy that amongst the plants regarded by Prof. Penzig

as introduced by frugivorous birds into Krakatoa since the eruption is a

species of Melastoma.

Few genera in these islands would better repay a careful study of their

species with regard both to the influence of station on specific

characters and to the question of “mutations” than OPHIORRHIZA. I found

the three Fijian species of this Rubiaceous genus so often in close

association, that I cannot doubt there is some connection between them.

Seemann and Gray, indeed, characterise two of them as confluent species.

The island of Tahiti alone possesses five peculiar species, and it is

evident that this island has been a centre of development for species of

Ophiorrhiza, just as Samoa has become the birthplace of many species of

the Urticaceous genus Elatostema. The minute angular seeds of

Ophiorrhiza would probably be transported in a bird’s feathers or in

adherent soil. As my experiments showed, they do not become adhesive

when wet.

The genus LORANTHUS as distributed in the South Pacific has already been

briefly noticed. There is a species confined to the Tahitian region, and

there is another peculiar to Samoa, whilst one widely-ranging species,

L. insularum, that connects these regions together, reaching east to

Rarotonga, is closely related with the Tahitian species. There was no

doubt originally a single polymorphous plant that ranged over the

tropical South Pacific. With regard to the mode of dispersal of the

seeds of this genus of parasites, I should at once refer to the

systematic and careful observations made by Mr. F. W. Keeble in Ceylon

(_Trans. Linn. Soc._, v. 1895-1901). He formed the opinion that the

seeds of Loranthus usually reach their host without passing through the

alimentary canal of a bird, being merely wiped off its bill. This method

would never carry the seeds to Tahiti or even to Fiji; and since this

observer remarks that, although most of the seeds in the droppings were

completely rotten, some of them “possibly pass through the gut

uninjured,” we may accept this possibility as sufficient for the purpose

of dispersal in the Pacific Ocean. Mr. Keeble notes the observation in

Teil 3 of Engler’s _Die Natürlichen Pflanzenfamilien_ that the seeds may

germinate after passing through a bird’s intestine; and we may therefore

infer that whilst the method he describes is typical of local dispersal,

the other method is required in the instance of oceanic dispersal.

ALSTONIA, an Apocynaceous genus of tropical Asia and Australia, yields

the caoutchouc of Fiji. Besides possessing in Fiji and Samoa peculiar

species, the islands of Western Polynesia have in A. plumosa a species

common to Fiji, Samoa, and New Caledonia. Another species, A. costata,

is restricted to Eastern Polynesia, occurring in the different islands

of the Tahitian Group as well as in Rarotonga. It is possible that the

Pacific species may be connected with A. scholaris, a species possessing

the range of the genus with the exception of Polynesia. The long

ciliated or hairy seeds, six to nine millimetres in length, are fitted

for transport by the winds and in birds’ plumage. The follicles dehisce

on the tree, and, according to Horne, the light seeds are distributed

locally by the wind. It is probable that the thick white juice oozing

from a broken branch would at times aid the adhesion of the seeds to a

bird’s feathers.

GENIOSTOMA, a genus of the Loganiaceæ, is found in Malaya, Australia,

and New Zealand. It possesses in G. rupestre a species that ranges

across the South Pacific from New Caledonia to Tahiti, being associated

with one or more endemic species in most of the groups. The fruit is a

dehiscent capsule containing numerous small seeds imbedded in a

yellowish pulp; and from the standpoint of dispersal it may be placed in

the same category with Pittosporum and Gardenia (see pages 310, 313).

The same principle involved in the occurrence of a species ranging the

South Pacific from New Caledonia to Tahiti, and associated with one or

more endemic species in most of the principal groups, is illustrated in

the Euphorbiaceous genus MACARANGA. It is specially noteworthy that M.

tanarius, which ranges from India to East Australia and the New

Hebrides, comes in touch in the group just named with M. harveyana, the

widely-ranging plant of the South Pacific above alluded to, and itself

an Asiatic species (see Burkill; _Bot. Chall. Exped._, iii. 191; _Index

Kewensis_). The connection between M. harveyana, the widely-ranging

species of the South Pacific, and the endemic species in the various

groups is indicated by its affinity with M. reineckei, a Samoan species.

The Macarangas in Fiji grow in a variety of situations, on the borders

of estuaries, in the mountain forests, and on the isolated mountain

peaks. It is to birds that we must look for the dispersal of the genus.

In the case of a species, apparently M. seemanni, common in the Rewa

delta, the seeds, which soon fall out of the cocci, are not infrequently

found in the drift of the estuary, but they sink in a week or two. Other

species examined showed no capacity for dispersal by currents. The fruit

of M. harveyana is provided with a few prickles, but since it breaks up

into the cocci, from which the seeds soon fall out, these appendages

could scarcely aid its dispersal.

Like many other genera, TABERNÆMONTANA, an Apocynaceous genus

distributed through the tropics, is represented in Polynesia by a

widely-ranging species, T. orientalis, which extends from Malaya and

Eastern Australia through all the large groups of the South Pacific from

the New Hebrides to Tahiti, and is associated in Fiji with one or two

peculiar species, one of which, according to Mr. Burkill, is nearly

related to it. This genus therefore seems to illustrate the earliest

stage in the Pacific of that process by which a widely-ranging species

takes on a polymorphous habit and through its variations gives rise to

different species in various groups. Prof. Schimper ranks T. orientalis

amongst the Malayan strand-flora; but in Fiji the Tabernæmontanas are

only littoral where the soil is rich as in alluvial regions; and they

have no capacity for dispersal by currents that is worth speaking of,

the seeds in the case of T. orientalis and another species sinking after

drying for years, whilst the follicles soon open in water and go to the

bottom in a few days. The observations of Gaudichaud and Moseley

indicate that some Malayan species are dispersed locally by the currents

(_Bot. Chall. Exped._, iii, 279, 293); but the fruits of the genus are

evidently quite unfit for oceanic dispersal by this agency. We find in

the bird the agent that has carried the genus to the distant

island-groups of the Pacific; and from the standpoint of dispersal the

fruits may be placed with those of Pittosporum and Gardenia, being

follicular, and in the Fijian plants possessing seeds, 5 to 10

millimetres in size, embedded in a pulp.

FAGRÆA, an Asiatic and Malayan genus of the Loganiaceæ, is represented

in the Pacific by F. berteriana ranging through all the groups and

islands of the South Pacific from the Solomon Islands and New Caledonia

to Tahiti and the Marquesas, and by one or two other species in Fiji. It

is with Fagræa berteriana that we are entirely concerned. The tree is

often planted by the Pacific islanders near their villages; and since

they value its timber and use its large fragrant flowers for personal

decoration and for other purposes, it is probable that they have aided

in its dispersal. But, as shown below, it behaves in most localities as

an indigenous plant; and its berries are well fitted for promoting its

dispersal by frugivorous birds.

I was familiar with Fagræa berteriana both in the Solomon Islands and in

Fiji; and in the last-named locality I especially studied it from the

standpoint of dispersal. All over the South Pacific, whether in the

Solomon Islands, in Fiji, in Rarotonga, or in Tahiti, this tree, though

thriving also in the lower levels, especially frequents rocky scantily

vegetated or open-wooded hill-tops and crests up to 2,000 or 2,500 feet

above the sea. In the rich alluvial soil of the Rewa delta in Fiji it

attains a height of 25 or 30 feet or more, whilst in the poor, dry soil

of the “talasinga” plains in this group it is much dwarfed, and often

does not exceed 10 feet, and may be only 6 feet high. It is in these

“talasinga,” or “sun-burnt,” plains of Fiji, especially in the Mbua

province of Vanua Levu, that the tree, although dwarfed, seems most at

home. Here it flowers and fruits abundantly whilst associated with

Acacia, Casuarina, and Pandanus trees, and it is in such dry localities

that this tree reflects in its choice of station the behaviour of

different species of the genus in the Malay Peninsula, where they grow

in open heath-country and sometimes on sandy heaths (Ridley in _Trans.

Linn. Soc. Bot._, iii, 1888-94). The fruits and seeds of F. berteriana

have little or no capacity for dispersal by currents. On the Fijian

plains the berries partially wither and rot on the tree. In the western

part of its area this tree almost comes in touch with the Asiatic

species, F. obovata, that ranges from India and Ceylon to the Malayan

region, a species that must be indebted to frugivorous birds for its

wide distribution.

The Euphorbiaceous genus BISCHOFFIA seems to offer another example of

polymorphism in a wide-ranging species. Following Drake del Castillo, I

take the genus as including only a single species, B. Javanica, a tree

distributed over tropical Asia, Malaya, and Polynesia as far east as

Tahiti. The variable character of the species is indicated by the

different views held by the several botanists who have discussed the

South Pacific species. Whilst it is a common forest-tree in Indo-Malaya,

it affects in the Pacific islands the open-wooded districts of the lower

levels, and it is not uncommon on the dry “talasinga” plains of Fiji.

The fruits and seeds displayed in my experiments little or no capacity

for dispersal by currents; nor do these dryish berries, with seeds four

or five millimetres long, seem to be especially attractive for

fruit-eating birds; and it is likely that the same birds that distribute

Macaranga seeds also disperse those of this genus. The tree bears the

same name over the South Pacific, “koka” in Fiji and Rarotonga, and “oa”

in Samoa. Like many other Polynesian trees, it has its uses, but there

is no reason to believe that the natives have aided materially in its

dispersal.

FICUS, a large genus comprising several hundred species, attains its

greatest development in tropical Asia and in Malaya. It is well

represented in the Western Pacific from the Solomon Islands to Fiji and

Samoa; but in Eastern Polynesia the species are very few, and the genus

is altogether absent from Hawaii, although a species has been found in

the North Pacific in Fanning Island, about 900 miles south of the

Hawaiian group (see page 377).

The Polynesian species are for the most part restricted to the Pacific

islands, but there are only two species that range over the South

Pacific as far east as Tahiti, namely, Ficus prolixa, the Tahitian

banyan, and F. tinctoria. Some species are confined to Western

Polynesia, such as F. obliqua, the Fijian banyan, F. scabra, and F.

aspera, the last occurring in East Australia. Among the individual

groups Fiji possesses probably fourteen or fifteen species, of which,

perhaps, a third would be peculiar. According to Dr. Warburg, as cited

in Dr. Reinecke’s paper, Samoa owns eight species, of which six may be

endemic. In Rarotonga and Tahiti we find only F. prolixa and F.

tinctoria. The species in the groups where they are best represented

belong to three or four sections of the genus.

The banyans of the South Pacific are represented by three or four

species, namely, Ficus prolixa, the Tahitian banyan, found all over the

tropical groups of the South Pacific from the New Hebrides and New

Caledonia to Tahiti, the Marquesas and Pitcairn Island (Maiden); F.

obliqua, the Fijian banyan, confined to the islands of the Western

Pacific from the New Hebrides to Tonga; and two new banyans in Samoa, as

described by Dr. Warburg in Dr. Reinecke’s paper. In my paper on

Polynesian plant-names it is shown that the banyans possess two names in

the Pacific, one being “aoa,” the Polynesian name, found in all the

groups from Samoa eastward, and connected linguistically with the

Malayan and Malagasy banyan-words; the other, the Melanesian name

typified in the Fijian “mbaka,” and represented in a variety of forms in

the New Hebrides and neighbouring groups.

It is probable that the Pacific islanders have assisted in the dispersal

of one or two of the species of Ficus, such as F. tinctoria, which they

employ for different purposes, but, generally speaking, birds are active

agents in distributing the genus. I need scarcely say that the agency of

the currents is quite insufficient to explain the distribution of Ficus.

When in Fiji I experimented on three or four different species of Ficus

belonging to the sections of the genus there represented. The fruits may

float at first, but within a week or ten days they break down, and the

seeds escape and sink. Beneath a tree of F. scabra growing on the banks

of the Wai Tonga in Viti Levu, I noticed a number of its fruits floating

in a sodden condition among the reeds at the river-side.

It is with the banyans that the dispersal of the seeds by frugivorous

birds becomes most evident. This is at once indicated by the frequent

occurrence of these trees in the interior of coral islets in the Western

Pacific, as in Fiji and in the Solomon Islands. Fruit-pigeons roost in

their branches, and birds shot on these islets often contain the fruits

in their crops (_Bot. Chall. Exped._, iv, 310). The process may also be

seen in operation in Krakatoa. Professor Penzig found in 1897 that three

species of Ficus had established themselves there since the eruption of

1883 through the agency of frugivorous birds. Besides pigeons, we find

that parrots, hornbills, honey-eaters, &c., feed on these fruits, and I

possess a large number of references to this subject. The Messrs. Layard

in New Caledonia, Dr. Meyer in Celebes, Mr. Everett in Borneo, Dr.

Forbes in Sumatra, and several other contributors to _Ibis_ might be

here mentioned. Dr. Beccari, in his _Wanderings in the Great Forests of

Borneo_, speaks of “the facile dissemination of the various species of

Ficus through the agency of birds,” and he arrives at certain important

conclusions which are discussed in Chapter XXXIII.

I have before alluded to the absence of Ficus from Hawaii. This group

possesses the Honey-Eaters (Meliphagidæ), birds well suited for

dispersing species of Ficus over Polynesia; but this family of birds is

only represented by peculiar genera in Hawaii, and therein lies the

explanation. At the time when the Honey-Eaters roamed over Polynesia,

the genus Ficus had not arrived from Malaya. The connection between the

bird and the plant is well shown on Fernando Noronha, which possesses a

peculiar species of Ficus and a peculiar species of dove, the only

fruit-eating bird in the island (Ridley).

THE ABSENTEES FROM TAHITI

Generally speaking, all the “difficult” genera which puzzle the student

of plant-dispersal in Fiji and Hawaii are absent from the Tahitian

region. Those with stone-fruits and with large seeds, where the stone or

seed is an inch in size and over, are absent from Tahiti. Thus the

genera Canarium, Dracontomelon, Myristica, Sterculia, and others, of

which the three first-named are known to be dispersed by fruit-pigeons,

have not advanced into the Pacific eastward of the Fijian region. We

miss in the Tahitian islands the large-fruited palms of Fiji, such as

the Veitchias with fruits two to two and a half inches (5 to 6 cm.)

long, and we find in their place a Ptychosperma, evidently very rare,

and the widely spread Pritchardia pacifica, that may have been

introduced by man, both with drupes not far exceeding half an inch (1·2

cm.) in size. The islands of the Tahitian region also lack the Coniferæ;

and genera like Dammara, Dacrydium, and Podocarpus that give such a

character to the Fijian forests are not to be found. In this region we

do not find many of the large-seeded Leguminous genera, such as

Cynometra, Storckiella, and Afzelia, that occur in Fiji, the only

large-seeded genera that it possesses being such as are brought by the

currents, namely, Mucuna, Strongylodon, Cæsalpinia. The difficulties

presented by the occurrence of the inland species of Canavalia and

Mezoneuron in Hawaii do not offer themselves in Tahiti (see Chapter XV).

Tahiti also lacks, as often before observed, the mangroves and most of

the plants of the mangrove-formation.

As above remarked, the Fijian trees with large “stones” and heavy seeds

an inch in size are not to be reckoned amongst the indigenous Tahitian

plants, “size” being an important determining factor in the exclusion.

The occurrence of Elæocarpus in Rarotonga presents no real difficulty,

as I have explained in Chapter XXVI. An apparent exception is presented

by the existence in Tahiti of Calophyllum spectabile, where the stones

are about an inch across; but since its fruits can float in sea-water

for nearly a month, and on account of the value placed on its timber by

the Polynesians, we cannot altogether exclude the agencies of man and

the currents. One seeming exception is also offered by the presence of

Serianthes myriadenia, a tree which in Fiji grows both in the forests

and on the banks of the tidal estuaries. Its seeds, which are six to

seven-tenths of an inch (15 to 18 mm.) in length, have no buoyancy, and

the pods float only two or three weeks. The case of Lepinia tahitensis

is alluded to elsewhere, but it may be added that these and other

difficulties await further investigation.

A great many Fijian plants are not found in the Tahitian region, such as

Micromelum, those of the order Meliaceæ, the Melastomaceous genus

Medinilla, Myrmecodia, Ophiorrhiza, &c., which are often quite as well

fitted for over-sea transport as are several of the plants already

established there. But it should be remembered that crowding out would

often come into play in such a contracted region. The area, however, has

been very generously dealt with as regards plant genera. Though the

total land-surface cannot be more than one-fourth or one-third that of

Fiji or Hawaii, it possesses more than half the number of genera found

in Fiji, and four-fifths of the number found in Hawaii.

FIJI

_The Fijian Genera not found in either the Tahitian or Hawaiian Regions_

We have already in some degree dealt with Fiji in so far as the partial

dispersal of genera over the Pacific islands is concerned. We have seen

that it possesses very few genera (not a score in all) in common with

Hawaii that are not found in the Tahitian region, and it is assumed that

in most cases such genera reached Hawaii independently and not through

the South Pacific. On the other hand, excluding the grasses, sedges, and

vascular cryptogams, Fiji owns in common with Tahiti between sixty and

seventy genera that do not occur in Hawaii. This shows unmistakably the

trend of plant migration in the Pacific islands. Several interesting

features in plant-distribution have been already brought out, and

notably the fact that Indo-Malayan genera with large seeds or “stones”

an inch in size have been arrested in the Fijian region in their passage

into the South Pacific. Thus Canarium, Dracontomelon, Myristica, and

Sterculia have not extended eastward of the Fijian area.

Yet a very large proportion of the Fijian genera, quite half of the

total number, are not represented either in the Tahitian or in the

Hawaiian region; and of many of them it is obvious that they are as well

fitted to be carried over the Pacific as are those that have actually

reached Tahiti and Hawaii. Take, for instance, Begonia, which has not

extended east of Fiji, though Hillebrandia, a genus of the order, is

peculiar to Hawaii. Nor can we explain why with three genera like

Geissois, Dolicholobium, and Alstonia, possessing seeds dispersed by the

winds, only the last-named has passed beyond Fiji. However, as before

remarked, it is probable that lack of opportunity rather than capacity

for dispersal has determined the matter, and we must, therefore, assume

that many of the genera have halted in the Fijian region because they

entered the Pacific after the age of active general dispersal over that

ocean.

Occasionally we notice in this region that which we have observed in the

case of Cyrtandra in different Pacific groups, namely, a sudden

development of what Hillebrand terms “formative energy” in a genus, such

as we find in the case of Elatostema in Samoa, and in that of Psychotria

in Fiji and Samoa. The principle of polymorphism in the development of

species is also illustrated by Micromelum and by Limnanthemum. In the

last case we possess a typical polymorphous species in Limnanthemum

indicum that has played in this respect the _rôle_ of Naias marina in

the warm waters of the globe.

With several genera that like Gnetum, Myristica, and Sterculia occur

both in the Old and the New World, it is evident that in explaining

their distribution we are dealing with something more than questions of

means of dispersal. With these genera, and with others like Lindenia, it

seems almost futile to talk of means of dispersal, when to all

appearance their existing distribution is but the remnant of an age of

general dispersion over the greater part of the warm regions of the

world. These genera, with others, might be cited in favour of the

continental hypothesis relating to the islands of the Western Pacific.

Trees with stone-fruits, such as Canarium, Couthovia, Dracontomelon, and

Veitchia, where the stones are an inch and more in length, might be also

adduced by some in evidence of this theory. But in these cases the

lesson of Elæocarpus (Chapter XXVI) should always be remembered, since

the “stones” of drupes may vary greatly in size amongst the different

species of a genus, and species seemingly “impossible” from the

standpoint of dispersal in one group may be represented in other groups

by species where the size of the “stone” presents no difficulty in

attributing the dispersal of the genus to frugivorous birds.

_Sterculia_

The problem connected with the presence of this genus in Fiji is but a

part of the still more difficult problem connected with the dispersal of

the genus over the tropics. The riddle presented by the Fijian species

seems, indeed, difficult enough; but it merely presents in miniature the

great mystery surrounding the whole genus. According to the _Index

Kewensis_ no other species have been found in oceanic islands except

those occurring in the Western Pacific, as in Fiji, the New Hebrides,

and New Caledonia, and most of these seem to be confined to those

islands. We have here a genus that repeats the Dammara difficulty of the

Western Pacific.

The trees are common in places in the Vanua Levu forests, where the

large, woody, open follicles may be seen lying in numbers on the ground,

empty and in all stages of decay. The seeds of one species, near

Sterculia vitiensis, were nearly an inch long and sank like stones. The

unopened follicles will float for weeks; but it is evident that Nature

does not disperse the genus in this fashion, since the fruits before

dehiscence remain on the tree. It is also noteworthy that Gaudichaud,

when describing the floating drift of the Molucca seas, refers to the

open follicles of two or three species of Sterculia (_Bot. Chall.

Exped._, iii, 279). The fruits never came under my notice in the drift

of Fiji. The seeds of a Fijian species examined by me were four-fifths

of an inch (2 cm.) long. They had a thin, brittle, outer skin and

crustaceous inner test, and, being edible, might attract birds; but such

birds would be ground feeders, like the Megapod, and the Goura pigeon of

New Guinea, and the Nicobar pigeon, birds of this habit being rare in

Fiji. I should doubt whether the seeds are sufficiently protected to be

preserved from injury in a bird’s stomach during a long sea-passage; and

they may thus be placed in the same category with the seeds of

Myristica, a genus that has also failed to reach Tahiti and Hawaii.

But the distribution of Sterculia raises other more important questions

than that connected with its occurrence in Fiji, which involves an

over-sea passage of only 500 or 600 miles. As in Podocarpus amongst the

Coniferæ, which has a similar distribution in the Western Pacific, we

have to explain the existence of the genus in the three great

continental masses of Africa, Asia, and America, now separated by oceans

several thousands of miles across. Here also we must look far back into

the ages for a common centre of diffusion in the extreme north, such as

is in a sense suggested by the occurrence of the order in the Eocene

beds of Europe.

As showing unmistakably that Fiji received its species from the Old

World, it may be observed that one of its trees, Sterculia vitiensis, is

very closely allied to S. fœtida, widely spread in tropical Asia, in

Malaya, and Australia, as well as in Africa.

_Trichospermum_ (Sterculiaceæ)

There are only two species of this tree recorded in the _Index

Kewensis_, one in Java, and one in Fiji as well as in Samoa. The fruit

is a capsule with small, flat seeds, margined by long hairs, that might

possibly attach themselves to a bird’s feathers.

_Micromelum_ (Rutaceæ)

This small genus of tropical Asia, Malaya, tropical Australia and the

islands of the Western Pacific, has one species, Micromelum pubescens,

possessing the range of the genus with other species that are restricted

to different localities. We thus have apparently another illustration of

the part played by a wide-ranging polymorphous plant in providing new

species. The red berries would easily attract frugivorous birds; but the

seed-tests seem too delicate to allow the seeds to remain more than a

few hours in a bird’s stomach without injury.

_Cananga odorata_ (Anonaceæ)

This tree, which is cultivated in many places in tropical Asia and

Malaya, but is certainly indigenous, according to the authors of the

_Flora Indica_, in Ava and Tenasserim, has apparently extended into the

Pacific by cultivation. But though much valued by the natives on account

of its fragrant flowers, and in consequence often planted by them near

their villages, it grows in some localities in Fiji and Samoa as an

indigenous plant. The berries are especially suited for dispersal by

frugivorous birds, their flat seeds, 8 mm. in length, possessing hard

crustaceous tests that would enable them to pass unharmed in a bird’s

droppings. According to Reinecke the fruits are sought after by pigeons,

and particularly by Didunculus strigirostris, the Samoan Tooth-Billed

Pigeon. The tree has not travelled eastward of Tonga and Samoa, with the

exception of its occurrence in Rarotonga; and according to Mr. Cheeseman

the Rarotongans received it from Samoa several years ago.

_Geissois_ (Saxifragaceæ)

This genus of seven or eight known species is found in Australia, New

Caledonia, the New Hebrides, and Fiji. Since New Caledonia possesses

four species, it may be considered the home of the genus. To the Fijian

endemic species, G. ternata, I paid special attention. The capsules

dehisce on the tree and allow the small seeds to escape. These seeds,

which are very light, 150 to 200 going to a grain, are 3 to 4 mm. long

and are winged at one end. They could no doubt be carried some distance

by strong winds; but they possess no buoyancy. Large bats probably aid

in their dispersal. The Fijians assert that these animals are in the

habit of visiting the trees for the sake of the honey furnished by the

conspicuous red flowers. When they see a bat flying towards these trees,

they are wont to remark that it is going to drink the “se ni vota,” that

is, to suck the flowers of the Vota tree. It is very likely that seeds

would sometimes be carried in their fur for considerable distances.

_Begonia_

Before the discovery of Hillebrandia, a new genus of the Begoniaceæ, in

Hawaii, the order was not known from Polynesia. However, in 1878 Mr.

Horne collected a species of Begonia in Fiji, and it was probably this

species that frequently came under my notice in the rain-forests of the

Vanua Levu mountains. In 1883 I collected a Begonia in the Solomon

Islands, which I gave to Baron F. von Mueller, who informed me that it

was the first record of the genus east of New Guinea, the description of

Mr. Horne’s Fijian plant apparently not having been published (see

Guppy’s _Solomon Islands_, p. 288). It is not easy to explain why a

genus with such minute seeds, which are apparently as well fitted for

dispersal as those of the orchids, should have such a limited

distribution in the Pacific.

_Dolicholobium_ (Rubiaceæ)

In the _Index Kewensis_ this genus, containing five species, is

restricted to Fiji. It must, however, be more generally distributed in

the Western Pacific, since the genus was identified at Kew among my

Solomon Island collections, and it is recorded in the list given in my

book on that group (pages 283, 288, 297).

The showy, large, white, fragrant flowers of these small trees recall

those of Lindenia, with which Dolicholobium is often associated in Fiji

by the sides of streams and rivers. As Horne observes, the Fijian

Dolicholobiums range from the sea-shores and the heads of the estuaries

to the tops of the highest mountains. As noticed by me in the Solomon

Islands they affected the same station, being especially common on the

banks of streams. The genus has a long, narrow capsule six inches or

more in length. The linear seeds, though very light, are an inch or more

long, the coats being drawn out into a long tail at either end, and thus

differing greatly from those of Lindenia, the other Rubiaceous genus,

with which these plants are so frequently associated at the river-side.

I can only suppose that the seeds are transported by the winds. The

history of the genus is suggested in my remarks on Lindenia.

_Lindenia_ (Rubiaceæ)

Respecting its distribution in the Pacific, this genus of showy

river-side shrubs takes the same place amongst the plants that Galaxias

takes among the fishes. It is full of mystery. Of the four species

known, two grow on the river-banks of Central America and two in similar

stations in the islands of the Western Pacific. Of the last-named both

occur in New Caledonia, one of them being endemic, whilst the other,

Lindenia vitiensis, is found also in Fiji and Samoa. Reinecke seemingly

records no Samoan species, but in the list of additions at the end of

his _Flora Vitiensis_, Seemann refers to the Fijian species as having

been found in Samoa by Dr. Graeffe.

Lindenia vitiensis, as Horne aptly remarks, adorns the rocky banks of

many Fijian streams with its cream-coloured flowers, which impregnate

the air with their sweet odour. I found it in Vanua Levu, both at the

heads of the estuaries and beside the stream and the torrent in the

heart of the mountains. It was often associated with a species of

Dolicholobium, which it resembled strangely in its large, showy, scented

flowers and in the form of the leaf. Seemann says it is also accompanied

at the river-side in Viti Levu by Ficus bambusæfolia and Acalypha

rivularis. It is noteworthy that all the four plants here mentioned as

being associated river-side plants in Fiji possess the long, narrow

leaves of the willow type, a subject that is discussed in note 79.

The capsules of Lindenia vitiensis contain numbers of small, angular

seeds about 1·5 mm. across, some 400 of them when well dried going to a

grain. The seeds float buoyantly by reason of their outer covering of

crisp, air-bearing, cellular tissue. When this outer covering is

stripped off, the minute nucleus, or seed proper, which is barely a

millimetre across and is but slightly protected, sinks at once. As the

seeds float on the surface of a stream they might readily get on the

plumage of an aquatic bird; but they have no special means of

attachment; though, if they dried on the feathers they might adhere to

some extent. That they could be carried in mud adhering to a bird across

an ocean’s breadth I think most unlikely; and it should be remembered in

this connection that only the dead or sickly seeds would be found at the

bottom of a stream.

The most reasonable explanation of the extraordinary distribution of

Lindenia is that it was in a past age found over the tropical regions of

both America and the Old World, and that it has died out over the

greater part of its original area. To study the means of dispersal of

plants with such a distribution seems almost futile. I am inclined to

think that the limited range of Dolicholobium, so frequently its

station-companion in Fiji, may be similarly explained.

_Limnanthemum_ (Gentianaceæ)

This interesting genus of aquatic plants is dispersed over the tropical

and temperate regions of the globe, but with the exception of Fiji and

the New Hebrides it is not found in oceanic groups, though it occurs in

large continental islands like New Caledonia and Cuba. About twenty

species are enumerated in the _Index Kewensis_, but it is stated in the

_Genera Plantarum_ that they can probably be reduced to ten, the

reduction being chiefly applicable to the tropical species, nearly all

of which are reducible to varieties of L. indicum, the temperate species

being often very distinct. It would thus appear that although dispersal

is still active in the tropics, it is in part suspended in the temperate

zone, and we seem to possess in L. indicum a typical polymorphous

species that has played the _rôle_ of Naias marina in the warm, fresh

waters of the globe (see page 368).

Although some of the temperate species, like Limnanthemum nymphæoides in

Europe and Northern Asia, have a wide range, it is probable that this is

connected not so much with means of dispersal, as with its relation to

present and past drainage-areas. Rivers in the lapse of ages change

their courses and carry their aquatic floras with them, leaving,

however, a few of their plants around the springs and in the lakes which

serve still as centres of dispersal. Rivers may even exchange their

plants in flood-time in extensive level districts. Nor is the occurrence

of the genus in the Old and New Worlds in the northern hemisphere to be

connected with questions of dispersal across an ocean. Except in the

case of small-seeded plants, like Nasturtium and Lythrum, where the

dispersal could be carried on by water-fowl, the plant-species being

often identical on both sides of the Atlantic, it is probable that most

of the large-seeded river-side genera common to Europe and North

America, such as Iris and Acorus, had in past ages their home in the

extreme north, whence the plants spread as from a focus into the

continents of America and Eurasia. It is also to be doubted whether even

in the tropics there has been much over-sea dispersal of Limnanthemum

without the aid of man, and reasons will be given for the belief that

probably in Fiji, in the New Hebrides, and in New Caledonia the seeds of

the first plants were unintentionally introduced by the aborigines.

Following Bentham we may regard the species of the Western Pacific

Islands as a form of the wide-ranging Limnanthemum indicum. These plants

in Fiji do not play the part in river-vegetation that they do in the

temperate regions, as for instance in the Upper Thames. They are not

common except in places, and seem to be chiefly confined to Viti Levu,

particularly to ponds in the Rewa delta, where their _rôle_ is that of

an Indian tank plant. In the Rewa delta they may be sometimes seen

thriving in brackish water having a density of 1·005.

Looking at the mode of dispersal to which the Limnanthemums owe their

existence in the Western Pacific, we cannot disregard, especially in

Fiji, the possibility of the seeds having been unintentionally

transported by the natives when they carried in their migrations their

edible tubers, such as Colocasia antiquorum, Alocasia indica, and

Cyrtosperma edulis, that are cultivated in wet places. It is in the

ponds around which these plants grow that the Limnanthemums thrive. The

Chinese, with their peculiar methods of cultivation, are now carrying

with them strange water-plants over the warmer regions of the globe; and

it would be surprising if the Pacific islanders in their migrations did

not do the same. If such an introduction, however, took place, it must

have happened before the time of Captain Cook, when the plant was found

in New Caledonia. (It may be remarked in this connection that the seeds

of the genus will germinate after being kept dry for years. Seeds of the

British species which I had kept dry for two and a half years germinated

healthily when placed in water.)

Some years ago I ascertained that the seeds of the British plants were

enabled, by means of their fringe of hairs, to attach themselves firmly

to the downy plumage of a bird’s breast. This could not happen with the

Fijian plant as the seeds are naked, and the same may be said of some

species described by Gray and Chapman as widely spread over the United

States. The seeds of the genus appear quite unsuited for safe transport

inside the body of a bird. The Fijians give the plants a variety of

names, nearly all of which are associated with the word for a duck, and

none of them bear an ancient impress. Thus we find such names as

“Ndambe-ndambe-ni-nga” and “Vothe-vothe-ni-nga,” meaning respectively

“the duck’s seat” and “the duck’s paddle.”

_Ceratophyllum demersum_

This wonderful aquatic has been dispersed over most of the globe; but I

will only mention its occurrence in oceanic islands, such as Fiji,

Samoa, the Bermudas, and the Azores, to indicate the necessity of

attributing its distribution in islands to birds. Several years ago I

made a careful study in England of the habits and mode of germination of

this plant, the results of which are given in _Science Gossip_ for

November, 1894; but reference can only be made here to such points as

bear on the occurrence of the plant in the Pacific islands.

It is well known that in our English ponds and rivers the plant

propagates itself, as a rule, by budding; and that it is only in

unusually hot and dry summers, such as that of 1893, when many ponds

became very low and were excessively heated, that the fruits mature in

any quantity. My observations clearly showed that a higher temperature

is required for the completion of maturation than for the early stage of

the fruiting process and for the flowering. After a comparison of my

river and pond temperatures, I formed the conclusion that whilst in

water 12 to 18 inches deep this plant requires for a week or more an

average daily maximum water temperature of 70° F. to produce its

flowers, a warmth of 80° and over is necessary to mature its fruit, a

condition to be found in England only in shallow ponds, where the plants

may fruit abundantly, but not in rivers, where they flower and rarely

mature the fruit (see also for the thermometric conditions my paper in

_Proc. Roy. Phys. Soc. Edin._, xii, 296). Since a yet lower temperature

(an average maximum water temperature of 66° for a week or more) is

sufficient for germination, it follows that the thermal conditions of

our English climate will allow Ceratophyllum to germinate and to flower,

though but rarely to mature the fruit.

Even in Fiji we can notice the distinction between the cooler river and

the superheated ponds and swamps of the Rewa delta as regards the

maturation of the fruit. In 1897 I found Ceratophyllum thriving in the

main channel of the Lower Rewa where the water was quite fresh; whilst

lower down where the water was often brackish its place was taken by

Ruppia maritima. In the main river, where the water unmixed with

sea-water rarely acquires a temperature of 80° F., the reading being

usually 78° to 79°, I never found the plants in fruit, and it is only in

the superheated shallow waters of the swamps and back-waters that they

mature their fruits.

Since Ceratophyllum even in tropical climates would probably only mature

its fruits in the superheated waters of shallow ponds, tanks, and

ditches, it follows that its dispersal by birds is confined to warm

regions. In the cold waters of the Siberian lakes and rivers it would

never mature its seeds, and could only be propagated by budding. If it

existed in the head-springs of the sources of a river in these

latitudes, it would be distributed by means of its floating shoots and

fragments along the length of the river basin, and in the times of flood

it might pass in the lower plains from one river system to another. When

rivers changed their courses it would be left behind in the lakes and

ponds and springs, and would also be carried away to the new region. In

this manner it would in the course of ages be distributed over a

continent without the aid of seed, propagating itself in a vegetative

fashion.

In the case of oceanic islands, however, we have to appeal to the seed.

Since the fruits sink in sea-water even after prolonged drying, and

since a few days’ immersion in sea-water, as I found, kills the floating

plant, we are driven to the agency of birds. The fruits, which without

appendages are a quarter of an inch (6 mm.) in length, are too large and

heavy to be carried in dry mud adhering to birds. The chances of their

becoming entangled in a bird’s feathers by means of their basal spines

and terminal style seem small, since they would be lying usually on the

mud under the water. They are quite fitted for safe transport in the

stomach and intestines of birds, such as is established in Chapter

XXXIII for Potamogeton and Sparganium in the case of ducks. As my

experiments show, drying for a period of three months does not injure

the germinating capacity of the seeds.

_Dracontomelon_ (Anacardiaceæ)

This is a genus accredited in the _Index Kewensis_ with eight species,

of which three belong to Borneo, one to Sumatra, one to Java, one to the

Philippines, and two to Fiji, all the species being restricted in their

range. My observations were confined to D. vitiense, Engler (D.

sylvestre in Seemann’s work), the Tarawau of the Fijians, who regard it

as a tree that is planted by the dead in Naithombothombo, the place of

departed spirits, according to the legend given by Hazlewood in his

Fijian Dictionary. Its method of dissemination in the Fijian forests is,

however, far more prosaic. Pigs and fruit-pigeons assist in the

dispersal of the seeds in these islands. Pigs are often found in the

vicinity of a Tarawau tree; and evidently they much appreciate the

fallen fleshy fruits, which are about 1-1/3 inch (3·3 cm.) across and

inclose a large stone 7/8 inch (2·2 cm.) in diameter. The entire fruit

and the detached stone sink in sea-water, the last floating only a few

hours, even after drying for four years. Mr. Hemsley regards the genus

as probably dispersed by the currents, since a stone was found amongst

the floating drift collected by the _Challenger_ Expedition off the

coast of New Guinea. The stone, however, is described as seedless, which

may explain its buoyancy. It is, however, to the fruit-pigeon that we

must look for the dispersal of this genus. In the crop of one of these

birds shot in Fiji I found the entire fruit of a Tarawau tree.

_Canarium_ (Burseraceæ)

This genus of trees, to which nearly a hundred species are referred in

the _Index Kewensis_, belongs mainly to tropical Asia and Malaya, a few

species occurring in tropical Africa, Madagascar, the Mascarene Islands,

and Polynesia. Its great home is in Malaya, to which two-thirds of the

species are confined; but its distribution in the oceanic islands of the

Indian and Pacific Oceans is especially interesting, Mauritius, Bourbon,

Fiji, Tonga, and Samoa (Horne) each possessing a species.

The large drupes of the genus, as I found in Fiji, have no capacity for

dispersal by currents; and we are, therefore, compelled to appeal to the

agency of the frugivorous bird. Yet to a person unaccustomed to the ways

of fruit-pigeons the transportation across a broad tract of ocean of

large heavy “stones,” an inch and more in size, would seem impossible;

and even to a student of dispersal improbable. Unless, however, we

prefer to accept the Lemurian theory for the Indian Ocean and the theory

of a Melanesian continent for the Pacific we are compelled to appeal to

these birds; and it can scarcely be said that our appeal is without some

justification. Both in the Solomon Islands and in the Fijis I was

familiar with the dispersal of the stones of these trees by

fruit-pigeons; and Wallace, amongst other writers, observed the same

long ago in the Malayan Islands (_Malay Archipelago_). Stones obtained

from the crops of Fijian pigeons measured 1-2/10 × 1 inch (3 × 2·5 cm.).

In the Solomon Islands these birds stock the interior of the coral

islets with trees of the genus, and the ground below the trees is often

strewn with the disgorged stones (_Bot. Chall. Exped._, iv, 310; Guppy’s

_Solomon Islands_, p. 85).

Although the difficulty concerned with the transport of the seeds across

a broad tract of ocean seems very great, it is quite possible that

further investigation will enable us to overcome this objection, just as

we have done in Chapter XXVI when explaining how the genus Elæocarpus

may have reached Hawaii. It is, indeed, not unlikely that, as with

Elæocarpus, the stones of the drupes may in some species be much smaller

and far more fitted for being carried in a bird’s body over several

hundred miles of ocean.

_Couthovia_ (Loganiaceæ)

Reference is here made to this genus because its mode of dispersal is

known, and because I was familiar with it in Fiji. Seemann gives two

species for Fiji, C. corynocarpa and C. seemanni, and the few other

species known seem to be confined to the Western Pacific. Solereder

gives a third species, C. densiflora, for Kaiser-Wilhelmsland in New

Guinea (Engler’s _Pflanz. Fam._ teil 4, abth. 2); and a Solomon Island

species, nearly allied to, if not a variety of, the Fijian species, C.

seemanni, is referred to in the list of plants from that group given in

my book on those islands. I found C. corynocarpa not infrequently

growing on the banks of small rivers in the heart of Vanua Levu. Its

drupes, which float for a few days in sea-water, are, according to

Seemann, eaten by fruit-pigeons. The “stone” varies from 2 to 4

centimetres (3/4 - 1-1/2 inch) in length; and from the standpoint of

dispersal the genus ranks with Canarium and Dracontomelon. Seemann

describes and figures this species, which was constituted by Gray, in

his _Flora Vitiensis_; but, apparently through an error, it is in the

_Index Kewensis_ accredited to Hawaii. Hillebrand makes no reference to

the genus in his book on the Hawaiian flora.

_Veitchia_ (Palmaceæ)

This genus of palms is closely allied to Ptychosperma, a Malayan genus

also represented in Fiji. The _Index Kewensis_ names four species, one

New Hebridean, and three Fijian. The fruits of two of the last-named

species tested by me had no floating power. The seed is about an inch

long, and the genus would be likely to be spread by fruit-pigeons. From

the standpoint of dispersal the genus would be placed with Canarium and

Couthovia; but possibly its presence in the Pacific may be indicative of

an ancient Western Pacific continent.

_Hibbertia_ (Dilleniaceæ)

This genus of some eighty known species is almost entirely Australian,

with the exception of a few species found in New Caledonia, Tasmania,

and apparently also in the Mascarene Islands. Horne was the first to

record a species from Fiji, where it grows commonly in the “talasinga”

plains on the lee sides of the islands, and also on the scantily

vegetated mountain summits. In Vanua Levu I often found these plants

growing on the rocky peaks of the highest mountains of the island, as on

Mbatini, 3,500 feet, and on Mariko, 2,900 feet. Their presence on these

isolated peaks can only be attributed to birds. The carpels contain one

or two seeds, which have a membranous aril; but in the plains the seeds

are usually destroyed by grubs.

_Myrmecodia_ and _Hydnophytum_ (Rubiaceæ)

These two genera of epiphytes, distributed over Malaya and extending to

the islands of the Western Pacific, possess tuber-like stems, which are

extensively chambered by ants that find a home in the interior. They

were familiar to me in the Solomon Islands, where they frequently grow

on the mangroves and on other littoral trees. They do not form such a

feature in the shore vegetation of Fiji, and judging from the

observations of Dr. Seemann and myself they occur most often on the

wooded mountain-peaks. The berries of these plants would attract

frugivorous birds; and their pyrenes, which in a Fijian Myrmecodia I

found to be 4 millimetres long, appear quite suitable for dispersal

through this agency. It would seem that germination may occur in the

berry on the plant. A specimen of Myrmecodia in fruit, that had been

lying overlooked for a fortnight between newspapers during one of my

mountain journeys, displayed on examination the pyrenes in a germinating

condition, the process being subsequently completed. The reader will

find these interesting plants described and illustrated in the English

edition of Schimper’s work on _Plant-Geography_, pp. 149, 150.

_Myristica_

The Nutmeg trees, though principally at home in Indo-Malaya, are found

also in the warm regions of Africa and America, as well as in the

islands of the Western Pacific from the Solomon group eastward to Fiji,

Tonga, and Samoa. The Tongan and Samoan groups possess two species in

common, whilst Fiji seems to possess its own species, four or five in

number.

The seeds of this genus have long been known to be dispersed by

fruit-pigeons. Mr. Moseley, in his _Notes of a Naturalist_, and in the

_Journal of the Linnean Society_ (vol. xv), tells us how at one time

these birds in their dissemination of the seeds in the Banda Islands

were active opponents of the policy of the Dutch Government in

preserving their monopoly of the cultivation of the nutmeg of commerce.

He found numbers of wild nutmegs in the crops of these birds in the

Admiralty Islands, some of which were partially digested and others

seemingly sound; and Mr. Hemsley includes the genus as amongst those

dispersed in the Western Pacific by birds (_Bot. Chall. Exped._, Introd.

46; iv, 229, 308). In my book on the Solomon Islands I refer to the

occurrence of these seeds in the crops of fruit-pigeons; and I found

that the seeds were similarly dispersed by these birds in Fiji. It is

likely that the absence of the genus from Eastern Polynesia is to be

partially connected with the insufficient protection of the seeds

against injury during such a long ocean passage in a bird’s body.

Gaudichaud, as quoted by Hemsley, refers to the occurrence of the fruits

of three or four species of Myristica in the drift floating in the

Molucca Sea. When in the Solomon Islands I noticed that the unopened

fruits of a species floated in sea-water. In later years in Fiji I

tested this point, and found that whilst the fruits just before

dehiscing will float between three and seven days in sea-water, the

seeds sink. As I have pointed out in the chapter on Drift, rivers carry

down to the sea an abundance of seeds and fruits that can float a few

days but do not imply dispersal by currents.

Although, as I have above remarked, the localised range of the genus in

Polynesia may be in part connected with the insufficient protection of

the seed, it is apparent that in the case of a genus found in Asia,

Africa, and America we are brought into contact with questions other

than those of means of dispersal. No one would pretend that Myristica

seeds could be carried by birds uninjured across the Pacific Ocean; and

to explain the present distribution of the genus we must recall cases of

a similar kind, such as Podocarpus, where the genus in past ages had a

home in the north, from which, as from a focus of dispersion, it

extended into the continents of the Old and the New World (see p. 302).

_Rhaphidophora_ (Araceæ)

This genus of climbing aroids, which gives a character to the forests of

Indo-Malaya as well as to those of the Western Pacific, is represented

in the New Hebrides, Fiji, Tonga, and Rarotonga by a variety of the

widely spread R. pertusa that ranges over Indo-Malaya and Eastern

Australia. The ripe berries would readily attract birds; and the seeds,

4·5 millimetres long in the case of a Fijian plant, appear hard enough

to pass unharmed through a bird’s digestive canal. We seem here to have

evidence of a somewhat recent connection between Indo-Malaya and

Polynesia through the agency of frugivorous birds. That the genus has

been long established in Polynesia is, however, indicated by the

occurrence there of a species seemingly peculiar to Fiji. We are

disappointed that in Engler’s recent contribution to the _Pflanzenreich_

(in his volume on the Araceæ-Pothoideæ) he has not been able to include

this genus in the field of his studies.

_Gnetum_ (Gnetaceæ)

This Gymnospermous genus, which is found in the warm regions both of the

Old and the New World, is represented in Fiji by a Malayan species,

Gnetum gnemon, which exists also in the Solomon group with other species

of the genus (Guppy’s _Solomon Islands_, pp. 288, 301). I was familiar

with this species in both Fiji and the Solomon group; but in the

first-named locality it is seemingly restricted to the borders of

Wainunu Bay on the south side of Vanua Levu, where Dr. Harvey first

found it. It grows there abundantly in young wood.

It seems almost idle to discuss the mode of dispersal of a genus that is

placed in a class apart with the African Welwitschia and the European

Ephedra, possessing with them a history of which we know nothing. Yet it

is ranked by Mr. Hemsley amongst those genera that are dispersed in

Polynesia by birds, and he produces better evidence in support of this

view than we possess for many other plants. Thus a fruit of a species of

Gnetum, perhaps G. gnemon, has been found in a New Guinea fruit-pigeon;

and the fruits of two species of the genus were found in the crops of

fruit-pigeons shot by Mr. Moseley in the Admiralty Islands (_Bot. Chall.

Exped._, Introd. 46; iv, 308). The red drupes of Gnetum gnemon of Fiji

would readily attract birds, and their nut-like stones, about 8

millimetres long, are well suited for this mode of dispersal. My

experiments in Fiji show that neither the drupe nor the stone of this

species floats in sea-water; and it is probable that the fruits of this

genus referred to by Mr. Hemsley as having been picked up on the beach

in the Aru Islands possessed only a temporary buoyancy.

This genus presents us with the same puzzling question put to us by

several Fijian genera, such as Myristica and Podocarpus, that occur in

both Asia and America; and until we answer that query it seems almost

futile to study modes of dispersal.

_Elatostema_ (Urticaceæ)

This genus of annual and perennial herbs belongs to the tropical regions

of the Old World. It is represented in Samoa by fifteen known species

and by at least four or five in Fiji, whilst with the exception of a

solitary Tahitian species it is not recorded from East Polynesia.

Reference is here made to it particularly on account of its great

development in Samoa. We have here a genus that, like Psychotria in Fiji

and Cyrtandra in Fiji, Samoa, and Hawaii, runs riot in respect to the

production of species (see p. 317). Dr. Reinecke describes fifteen

Samoan species, of which, with the exception of two found in Malaya, all

seem to be described for the first time. So sensitive, he remarks, is

the genus to external conditions that station-forms abound; and he

points out that if we were to follow the dividing lines usually

recognised between species, we should account every station-form a new

species. It is, of course, obvious that the polymorphism of the Samoan

Elatostemas depends primarily not on the varying influence of station

but on their sensitiveness to external conditions. One might put the

question to the Samoan Elatostemas that Hillebrand put to the Hawaiian

Cyrtandras, and ask why nature in this particular genus in this

particular locality thus luxuriates in formative energy. Almost every

Pacific group in respect of some of its plants presents the problem so

well stated by Dr. Reinecke for this genus in Samoa. It is noteworthy

that Schimper, in his work on _Plant-Geography_ (English edition, pp.

291, 297, 299), especially singles out Elatostema and Cyrtandra as

growing socially in the tropical rain-forests of Java and of the Asiatic

mainland.

_Scirpodendron costatum_ (Cyperaceæ)

As far as I can gather, this giant-sedge has not been previously

recorded from Fiji; but it is included in the Samoan flora, and has also

been found at Penang and Singapore, as well as in Borneo, Java, and

Queensland. In Samoa, as we learn from Reinecke, it grows both in the

coast swamps and on dry ground. In Fiji it is very common in the

mangrove-swamps at the mouths of rivers, especially in the Lower Rewa;

but in Vanua Levu it is also frequent in the marshy localities of inland

plateaux, 700 to 800 feet above the sea, as well as by the side of

streams in swampy districts on the lower hill slopes. This double

station in the salt-water swamp of the coast and in the fresh-water

marsh of the interior seems to be repeated in Java, where the plant was

first discovered by Zippelius on the banks of torrents in mountainous

regions and in swampy places.

The genus comprises, according to the _Index Kewensis_, only this

species, though variations are to be observed in plants from different

localities. The species was described by Kurz in the _Journal of the

Asiatic Society of Bengal_ (vol. 38, 1869) and by Bentham in his _Flora

Australiensis_; and an illustration is given by Miquel in his

_Illustrations de la Flore de l’Archipel Indien_ (1871). The plant is so

common in Fiji that one can only suppose that its resemblance to a

stemless Pandanus, from which, as Kurz observes, it is with difficulty

distinguished except when in flower or fruit, led to its being

overlooked by both Seemann and Horne. Its leaves, from 9 to 12 feet in

length, are commonly used for making mats and for thatching, both in

Fiji and Samoa. The plant usually attains a height of 3 to 5 feet.

The fruits occur abundantly in the floating and stranded river and sea

drift in Fiji, a circumstance that led to my discovery of the parent

plant in the swamps. The fruit, which is about half an inch (12 mm.)

long, consists of a hard, stony nut invested by a thick ribbed cork-like

covering, to which it owes its buoyancy, since the nut sinks. The

detached fruit is perforated at the base through both coverings, and

only a little soft tissue closes the aperture in the inner shell, the

protection against the entry of sea-water in the case of floating fruits

being quite inadequate. This explains also why the stranded fruits were

so frequently found by me germinating on the beach, where, as my

observations showed, they never established the plant. This early

germination would prove to be an advantage in the case of fruits

stranded in a suitable locality.

But though the perforation in the fruit favours its early germination,

it lessens its ability to withstand a long sea-passage without injury to

the embryo. I found in different experiments on fruits of plants growing

in the mangrove swamps, that when placed in sea-water 40 per cent. sank

during the first fortnight, whilst 15 per cent. floated after five or

six weeks, but all were at the bottom in two months. On the other hand,

fruits from plants of the swamps of the inland plateaux displayed much

feebler floating power, in some cases sinking at once, in others

floating for a few days, and in others again floating for a week or two.

In this case the outer cork-like covering proved to have lost most of

its floating power.

From the number of empty seed-vessels found, both in the floating and

stranded drift, it appeared evident that the seed had often rotted away

during the flotation. It is apparent from these observations and

experiments that Scirpodendron costatum is not suited for dispersal by

currents over wide tracts of ocean. The fruits might be able to float

unharmed for a few weeks, but they would be unable to accomplish much

more than the 500 or 600 miles intervening between Fiji and the nearest

groups to the west.

_Lemnaceæ_

This order, judging from the writings of Hegelmaier, Schenck, and

Hemsley, is represented by one or other of the common species, Lemna

minor, L. gibba, L. polyrrhiza, in various Atlantic islands, as in the

Bermudas, the Azores, Madeira, the Canary Islands, and St. Helena; but

doubts frequently arise as to their being truly indigenous. Lemna

trisulca is regarded by Hemsley as indigenous in the Bermudas. Lemna

minor has been introduced in recent years into Hawaii, where I observed

it flowering and sometimes fruiting abundantly in the heated waters of

the ponds. Two species found in other regions were recorded by Seemann

from Fiji, and I have come upon few other records of the occurrence of

the order in the tropical islands of the open Pacific. I am inclined to

the opinion, based not only on the facts of distribution, but also on

the results of numerous experiments on the means of dispersal, that this

order has in most cases reached oceanic islands with man’s assistance.

Some years ago I made a systematic study of the habits of the British

Lemnæ, most of the results being published in the _Linnean Society’s

Journal_ (vols. xxix and xxx), as far as concerned Lemna minor, L.

gibba, and L. polyrrhiza. During this inquiry I ascertained that with

these species, as well as with L. trisulca, the chances of a bird’s

carrying their fronds uninjured in its plumage over a wide extent of

ocean were small. None of them survived twenty-four hours’ drying in

fine weather, whether in the sun or in the shade; but in rainy weather

they withstand an exposure of one or two days. It is, therefore,

unlikely, even if the fronds were entangled by their rootlets in a

bird’s feathers, that they would be able under ordinary conditions to

reproduce the plants after a day’s flight of some five hundred miles

across the sea. It must also be remembered that the drying capacity of

the air when a bird is in full flight in ordinary weather would be that

displayed during a gale of wind with a velocity of at least thirty to

forty miles an hour. For this reason I do not think with Kerner that

under usual conditions drops of water would be a factor of importance in

causing the adherence of minute seeds of any kind to birds’ plumage.

Where the seeds are not available, it is most probable that birds

disperse the duckweeds by their fronds over short distances, but not

across broad seas. This would certainly apply to temperate latitudes,

where these plants rarely seed. Thus with Lemna, as with Ceratophyllum,

it would seem that the dispersal of the seeds by birds takes place

normally only in warm latitudes. Those of the duckweeds could be

transported in adherent mud over land-areas.

According to Hegelmaier, the two species of Lemna found in Fiji are L.

paucicostata, an Asiatic species, and a variety of an Australian

species, L. oligorrhiza, possessing dark root-sheaths. These plants

mostly came under my notice in the Rewa delta. They were rarely seen in

Vanua Levu, where in one locality I found the typical Lemna minor. The

first species is also Samoan.

In 1897 and in 1899, in a pool near Notho in the Rewa delta, in Viti

Levu, Fiji, I found a great abundance of a species of Wolffia, specimens

of which were sent to Prof. Schimper with my mangrove collections, but

his death intervened, and I have not been able to follow up the matter.

On comparing the specimens with Hegelmaier’s descriptions and plates, it

would seem that the species is near W. arrhiza and W. brasiliensis, but

differs from both in the greater length of the fronds. As concerning the

means of dispersal of the genus, I may add that the fronds were killed

after being allowed to dry for eighteen hours.

_Marsilea_ (Marsileaceæ)

A species of this genus, apparently near Marsilea villosa, was common in

the ditches and ponds around Notho, in the Rewa delta, Fiji, in 1897-99.

The genus is included by Horne in his list of Fijian plants; but is not

given by Seemann. The villous sporocarps, when dry, are very light and

readily catch in cloth and in feathers. Hillebrand includes in the

Hawaiian flora M. villosa and M. crenulata. The first-named, which was

collected by Chamisso and Gaudichaud, finds (he says on the authority of

Braun) its nearest relative in a species from Oregon and California. The

other has been collected in the Liukiu Islands, the Philippines,

Mauritius, and Bourbon. It is very probable that the occurrence of the

genus in oceanic islands is due to the agency of birds.

_Summary of the Chapter_

(1) We are here concerned with the more restricted distribution of

non-endemic tropical genera over the Pacific. The general trend eastward

of these genera is well brought out in the fact that whilst Fiji

possesses some sixty or seventy genera in common with Tahiti to the

exclusion of Hawaii, it does not possess a score in common with Hawaii

to the exclusion of Tahiti. The grasses and sedges and the mountain

genera are not here included; and we are comparing the flora of the

Hawaiian lowlands below 4,000 feet with the floras in mass of Fiji and

Tahiti.

(2) Hawaii possesses very few genera (less than thirty) that are not

found either in Fiji or in Tahiti, or in both; and of these quite a

third are to be traced to America.

(3) From two of these genera, Embelia, a land genus, and Naias, an

aquatic genus, we obtain two important indications, namely, that

specific differentiation has taken place to much the same extent in a

water plant as in a land plant, whether in a continent or in an island.

In other words, new species have been developed or are developing

independently of the immediate environment and of isolating influences.

(4) The interchange of plants between the regions of Hawaii and Tahiti

to the exclusion of Fiji has been very slight. Probably not half a dozen

genera belong to this category.

(5) Excluding plants brought by man and by the currents, Tahiti

possesses very few that present any difficulty from the standpoint of

dispersal, plants with seeds or “stones” an inch in size being, as a

rule, absent.

(6) With the genera (60-70) common to Fiji and Tahiti, and distributed,

therefore, over the South Pacific, the wide-ranging highly variable

plant is an important factor in the development of peculiar species in

the different groups, just as it has been shown to be in the previous

chapter in the case of genera dispersed over the whole Pacific. The

_rôle_ of the polymorphous species has always been an important one in

this region.

(7) In the case of several Fijian genera it seems almost futile to talk

of existing means of dispersal, since the present distribution of genera

like Sterculia and Gnetum, that occur on both sides of the Pacific, in

America and in Asia, is not to be thus explained.

(8) On account of the large size of their seeds and “stones” it might be

argued that certain of the Fijian plants afford evidence of a previous

continental condition of the islands of the Western Pacific, since it is

not easy to understand how such large seeds and “stones” could have been

transported over broad seas by birds. It is, however, pointed out that

in these respects the species of a genus may vary greatly, and that the

seeds and stones may be large in some species and small in others.

(9) 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;

and 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 that at first comprised the whole of the tropical Pacific was

afterwards restricted to the South Pacific, and finally to the Western

Pacific only. The birds that in an early age 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 of the bird have

taken place together.

CHAPTER XXVIII

THE POLYNESIAN AND HIS PLANTS

Identity of the problems presented by the indigenous plants and the

peoples of the Pacific islands.—The food-plants of the Polynesians and

the pre-Polynesians.—Their weeds.—The aboriginal weeds.—The white

man’s weeds.—Weeds follow the cultivator but are distributed by

birds.—The general dispersion of weeds antedates the appearance of the

Polynesian in the Pacific.—Weeds of little value to the

ethnologist.—Aleurites moluccana.—Inocarpus edulis, Gyrocarpus

Jacquini, Serianthes myriadenia, Leucæna Forsteri, Mussænda frondosa,

Luffa insularum.—Summary.

MAN AND THE SEED

MAN in his distribution in the islands of the Pacific reproduces in a

minor degree nearly all the difficulties presented there by plants,

birds, and other forms of animal life. Like the plant he entered the

ocean from the west; and as with the plants, so with the aborigines,

there was an era of general dispersion over this ocean, followed by an

age in which Polynesian man, ceasing to migrate, tended to settle down

in the several groups, there undergoing differentiation in various

respects, as in physical characters, in language, and in manners. Just

as we can now recognise the type of a plant, of a bird, or of an insect,

that belongs to a particular group of islands, so we can distinguish

between the Hawaiian, the Tahitian, and the Maori, whether in physical

characters, in his speech, or in his customs. Fiji possesses in the

Papuan element of its Melanesian population the earliest type of man in

the Pacific, just as it also possesses in the Coniferæ the most ancient

types of trees in this region. Divesting his mind of all previous

conceptions, the ethnologist, as I have remarked in my discussion of the

distribution of Freycinetia in Chapter XXV, might profitably study _de

novo_ the dispersion of man in the Pacific from the standpoint of

plant-dispersal.

Man and the seed have battled their way over the Pacific apparently in

defiance of the prevailing winds and currents, and both have failed to

reach the New World. Man in the Pacific is almost as enigmatical as the

plant. As a denizen of this region he is by no means a recent

introduction; and though his food-plants are mainly Asiatic, they belong

to distinct ages in the history of man’s occupation of these islands.

I venture to think that a great deal lies behind the Indo-Malayan mask

of the Polynesian, and that there is a story concerned with his origin

that has yet to be told. We have by no means solved the riddle when by

following the evidence we assign to him a home in Asia. It is only then

that the real difficulties begin. It required many centuries of European

civilisation for the discovery of America; but the voyages of Columbus

sink into insignificance when we reflect on what had been dared and

accomplished by uncivilised man when he first landed on the shores of

Hawaii and Tahiti.

The problem of man in the Pacific bristles with difficulties differing

in degree but not in kind from those relating to the flora. Whenever a

particular theory seems on the point of being well established, some

disturbing question arises, and as with the plant, we are never able to

push our facts quite home. Since I first visited the Solomon Islands,

now twenty-four years ago, the Pacific islander and his flora have

deeply interested me. The history of man and of the plant cannot be

separated in the Pacific; and the same determining principles of

distribution have affected both.

THE FOOD-PLANTS OF THE POLYNESIANS AND PRE-POLYNESIANS