With regard to the absence of these arbo_Observations of a Naturalist in the Pacific Between 1896 and 1899, Volume 2 Plant-Dispersal

island-groups of the Western Pacific, and notably from Fiji and Samoa,

where no members of the order seem to occur, it is probable that, as in

the case of the similar distribution of the early Compositæ described in

the preceding chapter, this is to be attributed to the fact that the

Western Pacific archipelagoes were more or less submerged during the

general dispersion of the Compositæ and Lobeliaceæ over the Pacific in

the earliest age of the floral history of these islands. The occurrence

of the early Compositæ and Lobeliaceæ in Rarotonga, which is almost

half-way between Tahiti and Tonga on the outskirts of the Fijian region,

sufficiently indicates that they are not lacking in that region from

inability to reach there in the past. During the age of general

dispersal of these two orders over the Pacific, probably only a few

rocky islets, tenanted perhaps by Conifers, marked the situation in the

Tertiary period of the present archipelagoes of Fiji and Samoa.

One may note in passing the general absence of these arborescent types

of the Lobeliaceæ from Malaya, since they do not seem to have been

recorded either from the Owen Stanley Range in New Guinea or from

Kinabalu in North Borneo, the highest mountain in the Malayan Islands,

or from the mountains of Java.

The consideration of the occurrence of these plants in other tropical or

subtropical oceanic islands need not detain us long, since, with the

exception of the solitary Lobelia scævolifolia of St. Helena, they seem

rarely to be found. This species, which is endemic, is a shrub growing

on the upper slopes and summit of the island at elevations of 2,000 to

2,700 feet (_Introd. Bot. Chall. Exped._, p. 40, and Part ii. pp. 54,

76).

There are two herbaceous species of Lobelia in Juan Fernandez, of which

one only, according to Hemsley, could be regarded as indigenous. This is

a showy Chilian and Peruvian species (Lobelia tupa) noticed by Bertero

as very common in 1829 (_Bot. Chall. Exped._, Part iii.). Since,

however, it would belong to the present age of plant-dispersal in the

Pacific, it does not require further mention here; and indeed it would

almost appear, when we bear in mind the geographical position and the

history of this island since its discovery in 1563, that even as a truly

indigenous plant it is not above suspicion. Lobelias of this type are

now amongst the commonest plants of the coast regions of northern Chile,

where I noticed some as much as 9 or 10 feet high.

_On the Capacities of Dispersal of the Lobeliaceæ of the Pacific._—Of

actual observations, with the exception of the instance of birds pecking

at the capsules of our garden Lobelias, I have come upon few that bear

directly on this point. When writing of the flora of the Kermadec Group,

many years ago, Sir Joseph Hooker referred (_Journ. Linn. Soc. Bot._,

vol. i.) to the minute seeds of Lobelia as not adapted for transport

unless their minuteness and number fit them for it; but since he

associates in this connection the tiny seeds of Metrosideros, which is

now represented by a species found all over the Pacific, it would seem

that the difficulty in the case of Lobelia is not connected so much with

the nature as with the suspension of these means of distribution during

the later stages of the plant-stocking of the oceanic islands of the

tropical Pacific. It will be gathered from the following remarks that

the descendants of the early Pacific Lobeliaceæ are probably as well

fitted for dispersal as their ancestors, and that the break in the

communication is the ultimate subject for inquiry.

The fruits of the Hawaiian endemic genera are in four out of five cases

baccate, with usually fleshy or pulpy contents. Such berries, which are

generally yellow, but sometimes bluish in colour, vary in size from

about half an inch in Rollandia and Delissea to an inch in Cyanea, and

not infrequently to more than an inch in Clermontia. The fruits of

Lobelia and Brighamia are capsular and dehiscent. With regard to the two

genera of the Society Islands and Rarotonga, the fruits of Sclerotheca

are hard-walled capsules, opening by two pores; whilst those of Apetahia

are seemingly dry and indehiscent. I do not imagine, therefore, that the

character of the fruit has determined to any important degree the

distribution of these plants.

Nor is there reason to suppose that the fruits have acquired their

baccate character in Hawaii, and that they were originally dry and

capsular. Both types of fruit are found among the arborescent Lobeliaceæ

of America, with which the Hawaiian genera have their affinities.

Centropogon, for instance, which occurs in Central America and in the

warm parts of North and South America, has, according to Baillon, a

somewhat fleshy berry. It is noteworthy that a similar question is

raised with respect to Cyrtandra as to the relation between fleshy

fruits in the Pacific islands and dry or capsular fruits in the

continental home of the genus (see Chapter XXV.).

The berries of the Tree-Lobelias would attract birds. We learn from Mr.

Perkins that one of the Hawaiian Drepanids, the Ou, is very partial to

the berries of some of the Tree-Lobelias and especially those of

Clermontia, the seeds passing unharmed in the droppings. The mode of

dispersal of the seeds of the dry-capsular fruits is not so apparent;

but the fruits could scarcely be less inviting to birds than the dry

capsules of Metrosideros, the small seeds of which have in some way or

other been carried to almost every island-group of the Pacific. I have

beside me the dark brown, smooth crustaceous seeds of a species of

Clermontia. They measure 1/42 of an inch or 0·6 of a millimetre, and

about 500 go to a grain. Mr. Wallace, in his book on Darwinism,

advocates the paramount influence of winds over birds for carrying small

seeds, like those of Orchis and Sagina, over tracts of ocean a thousand

miles across. I am, however, not inclined to think that, except as

regards the spores of cryptogams, winds have done very much for Hawaii.

For small seeds we can appeal not only to the agency of birds and bats

but also to insects (see Chapter XXXIII.).

Observations of this kind, however, merely indicate that these early

Lobeliaceæ possessed the same capacities for dispersal that in the

succeeding stages of the plant-stocking of the Pacific islands have

belonged to Metrosideros, Cyrtandra, Ophiorrhiza, Freycinetia, and many

other small-seeded genera. They go no way to explain why the same

agencies which transported the minute seeds in a later age could not

have been available for continuing the dispersal of the early

Lobeliaceæ. To find an explanation we are compelled to go behind the

mere capacities for dispersal and to appeal to the general laws of

distribution in so far as our facts enable us to interpret them.

We have seen that the two principal components of the early Pacific

flora, the Compositæ and the Lobeliaceæ, have American affinities. The

plants of the later ages are mainly Old World in their connections.

Though containing often endemic species in the various groups, the

genera occur also outside each group. The stream of migration that came

from America during the early age of the Compositæ and the Lobeliaceæ,

when the islands of the Western Pacific were more or less submerged, was

during the later ages (after these islands had re-emerged) suspended or

diverted, giving place to a stream that brought plants in numbers from

tropical Asia, Malaya, and Australia. The general dispersion of the

Compositæ and Lobeliaceæ took place during the Tertiary submergence of

the islands of the Western Pacific, including the island-groups of Fiji,

Samoa, and Tonga. The migration from the west, mainly Indo-Malayan in

character, occurred after the re-emergence of those archipelagoes. Thus

we get to understand how genera like those of the early Lobeliaceæ and

Cyrtandra, which possess, as regards the minute size of their seeds,

closely similar capacities for dispersal, have such different

distributions, the first confined to Hawaii and Tahiti and American in

their affinities, the second widely spread over the Pacific with its

home in Malaya.

We have yet to inquire whether this suspension of the means of transport

in the later ages of the Pacific Lobeliaceæ is confined to the tropics

or whether it extends to the colder latitudes in the southern

hemisphere. The indications of the Lobeliaceæ of the “antarctic flora”

go to establish that the dispersal of the order is still, or was very

recently, in operation in these high latitudes. It is well illustrated,

among other plants, by Lobelia anceps, which is found in extra-tropical

South America, Australia and New Zealand, and South Africa. This,

indeed, recalls Bentham’s view concerning the Compositæ, that whilst

communication was broken off in the tropics, it was kept up in higher

latitudes.

Here ends, therefore, our consideration of the Tree-Lobelias of the

Pacific islands; but as it is not quite complete without a discussion of

the remaining endemic genera of other orders than the Compositæ and

Lobeliaceæ which also belong to the same early age of the Pacific

floras, I will proceed at once to their consideration.

THE HAWAIIAN ENDEMIC GENERA EXCEPTING THOSE OF THE COMPOSITÆ AND

LOBELIACEÆ.

It will not be possible for me to do more than point out a few general

indications that can legitimately be drawn from these genera. The

subject bristles with difficulties for the systematist; but on one point

there can be but little danger of going astray, namely, in imputing to

them a high antiquity in the floral history of Hawaii. This can be said

of all of them, whether or not the generic distinction adopted in Dr.

Hillebrand’s work is always adopted by botanists. It is therefore in

this general sense that they may be regarded as belonging to the early

age of the Hawaiian flora.

Although the genera of Compositæ and Lobeliaceæ are prominent amongst

the representatives of the original flora of the Hawaiian Islands,

forming about two-fifths of the whole, the genera of other orders are by

no means inconspicuous, and their variety is shown in the fact that

though twenty-three in number they belong to twelve orders. It is

possible to divide these genera into two groups—one the older and

perhaps more or less contemporaneous with the Lobeliaceæ and Compositæ,

the affinities when apparent being American; the other the more recent

and marking the close of the first era of the plant-stocking of these

islands, the affinities being all with the Old World, and especially

with Malaysia. This grouping is indicated in the list subjoined; and it

may be here remarked that whilst shrubs, undershrubs, and perennial

herbs of the Caryophyllaceæ, Labiatæ, and Urticaceæ form the features of

the earlier group, trees of the Rubiaceæ and Araliaceæ are the most

conspicuous members of the later group. At the close of the earliest era

known to us of the floral history of the Hawaiian Islands we observe the

commencement of those forests that now throughout Polynesia as well as

in Hawaii betray their Asiatic origin.

In making this distinction I am proceeding on the assumption that the

stream of migration, at first chiefly American in its source, came

ultimately in the main from the Asiatic side of the Pacific. The change

commenced, as I hold, in the latter portion of the first era of

plant-stocking, an era characterised by the arrival of those early

plants that are now represented by the endemic genera of the

archipelago. The genera of this early period that belong neither to the

Compositæ nor to the Lobeliaceæ are, as above observed, arranged by me

in two groups, one regarded as contemporaneous with, the other as of

later origin than, the genera of these two orders. To the first belong

the shrubby, highly differentiated genera of the Caryophyllaceæ,

Schiedea and Alsinidendron, and the Labiate genera, similarly

differentiated, of Phyllostegia and Stenogyne. To the second belong the

Rubiaceous genera Kadua, Gouldia, Bobea, and Straussia, the Araliads

Cheirodendron, Pterotropia, and Triplasandra, and the Loganiaceous

Labordea.

In the earlier group the fruits are dry in half the genera, and in such

cases granivorous birds probably were usually the transporting agents.

Only in one case (Nothocestrum) is the fruit a berry, and in the other

cases we have fruits like the fleshy nucules of Phyllostegia and

Stenogyne which would probably attract birds. In the later group

two-thirds or three-fourths of the genera have moist fruits such as

would be eaten by frugivorous birds. Of these most are drupes,

possessing not a single stone, but two or more pyrenes. This is the

first appearance of the drupe in the plant-history of the archipelago.

The Rubiaceous type of drupe inclosing two or more pyrenes plays a very

conspicuous part in the distribution of plants over the Pacific in the

succeeding eras.

I would here lay stress on an important characteristic of all the fruits

of the endemic genera of the Hawaiian Islands. There are no “impossible”

fruits of this era in Hawaii, such as we occasionally find in the

succeeding eras. I mean by this term, fruits that defy the efforts of

the student of distribution to explain their transport in their present

condition. The discovery of a new inland genus possessing dry

indehiscent fruits three or four inches long, or even of a single

species of the coniferous Dammara, would play havoc with all our views

respecting the stocking of these islands with their plants. The finding

here of a large marsupial would scarcely produce more astonishment. The

fruits indeed of this early era are very modest in their size, the dry

indehiscent fruits and the stone-fruits rarely exceeding half an inch

(12 mm.) in size.

There is another interesting point which is connected with the

deterioration of some of the fruits in their capacity for dispersal.

Some of the species of Phyllostegia, and a few also of the Araliads, as

well as those of Nototrichium, are ill fitted for dispersal by birds

now, the coverings of the seeds being not sufficiently hard to protect

them from injury in a bird’s stomach. At the same time there are in some

cases other species of the same genera that are better suited for this

mode of transport. The effect of dispersal by frugivorous birds is that

only the hard-coated seeds propagate the plant in a new locality. When,

however, as has occurred in the Hawaiian Islands, bird-agency largely

ceases to act, this selective influence is removed (see Note 68).

ENDEMIC HAWAIIAN GENERA, EXCLUDING THOSE OF THE COMPOSITÆ AND

LOBELIACEÆ, AS GIVEN IN HILLEBRAND’S “FLORA OF THE HAWAIIAN ISLANDS.”

[Those preceded by * are not usually regarded now by botanists as

endemic, though they nearly

take that rank.]

THE EARLIER GROUP.

+-----------------+---------------+---------+------------+-----------------+-----------------------------+

+-----------------+---------------+---------+------------+-----------------+-----------------------------+

| | | | | | |

|Schiedea |Caryophyllaceæ.| 17 |Undershrubs,|Capsule. {|Near Colobanthus of the |

| | | | &c. | {| Antarctic islands, temperate|

|Alsinidendron |Caryophyllaceæ.| 1 |Undershrubs.|Capsule, with {| South America, |

| | | | | fleshy calyx. {| and Australia (C). |

|*Phyllostegia | Labiatæ. | 16 |Undershrubs.|Fleshy nucules. {|Belong to the tribe Prasiæ, |

| | | | | {| which is mostly Asiatic. |

|Stenogyne | Labiatæ. | 17 |Trailers or |Fleshy nucules. {| Two other species of |

| | | | climbers. | {| Phyllostegia recorded |

| | | | | {| from Tahiti and Paumotu |

| | | | | {| Islands. |

| | Worlds. |

| THE LATER GROUP. |

| | | | | | |

|*Pterotropia | Araliaceæ. | 3 |Trees. |Drupe. {|Malayan (H). |

| | | | | {| Pterotropia referred to |

|Triplasandra | Araliaceæ. | 4 |Trees or |Drupe. {| Heptapleurum of Old |

| | | | shrubs. | {| World (IK). |

+-----------------+---------------+---------+------------+-----------------+-----------------------------+

(H) = Hillebrand’s _Flora of the Hawaiian Islands_.

(IK) = _Index Kewensis._

NOTE.—Probably Schumann’s genus, Pteralyxia, should be placed in the

later group (see p. 154).

Another feature of interest is to be found in the distribution within

the archipelago of the species of the peculiar genera. As in the case of

the Compositæ and Lobeliaceæ, but few of the species are generally

distributed, most being restricted to one island or to two or three

adjacent islands. The suspension of the dispersal among the islands is,

however, not so marked as with the species of the two orders just named.

NOTE.—Some further remarks on some of these genera are given in Note 68.

THE ENDEMIC GENERA OF THE FIJIAN ISLANDS.

The interest that is associated with the endemic genera of Hawaii fails

to attach itself to those of Fiji. For this there are several reasons.

In the first place, our acquaintance with the Fijian flora is much less

complete. In the next place, the group holds a much less isolated

position, and the history of an endemic genus may have a significance

quite different from that connected with it in Hawaii. Fiji also lacks,

on account of its submergence in the Tertiary period, those highly

interesting genera of the Compositæ and Lobeliaceæ that form the chief

feature in the early history of the flowering plants of Hawaii. Then,

again, on account of our imperfect knowledge of the floras of the

neighbouring groups of continental islands to the westward, the New

Hebrides, Santa Cruz, and Solomon Groups, we can never feel quite

confident that any particular genus is really peculiar to the Fijian

archipelago. This is well brought out in the later history of the genera

designated by Dr. Seemann in his _Flora Vitiensis_ as peculiar to Fiji.

Of the sixteen genera enumerated by Dr. Seemann, and given in the table

below, only about half now retain their character of being restricted to

Fiji. Nor does it seem likely that future investigations will increase

this number, since, judging from a remark made by Mr. Hemsley in his

paper on the botany of the Tongan Group, explorations subsequent to

those of Dr. Seemann, more especially those of Mr. Horne, have not

apparently added a single new endemic genus to the Fijian flora. It will

be seen from the list that at least four of the sixteen genera have

since been found in the Malayan region, and in one case (Smythea

pacifica) the same species occurs in both regions; whilst a fifth genus

(Haplopetalon) has been recorded from New Caledonia.

There are, however, some peculiarities about the Fijian endemic genera

that will attract our attention from the standpoint of dispersal. One

remarkable feature is the paucity of species. Almost all the genera are

monotypic, that is to say, they are only known by a single species.

Amongst the twenty-eight Hawaiian genera that are strictly endemic, only

four or five are monotypic, and they are mostly regarded by Hillebrand

as worn-out, decadent types found in only one or two islands. In Hawaii

there are on the average six species to each endemic genus; and it is

thus apparent that in the display of formative energy Nature has worked

on very different lines in these two groups. Since the nine Fijian

endemic genera belong to nearly as many different orders, the

composition of this endemic generic flora is by no means homogeneous. It

is, I venture to think, such a motley collection as one might expect in

a region that has been exposed to wave after wave of migration from the

west, with no lofty mountains, as in Hawaii, to afford a refuge against

extinction. It by no means follows that all these endemic genera have

been produced in Fiji. Some of them may represent genera that have

become extinct in the large continental groups to the westward.

SEEMANN’S SIXTEEN FIJIAN ENDEMIC GENERA.

+--------------+------------------+---------+-----------+-----------+-------------------+

+--------------+------------------+---------+-----------+-----------+-------------------+

| | | | | | |

| | | | | | |

| | | | |capsule. | (S). |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | (IK). |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | (IK). |

| | | | | | |

| | | | | | |

| | | | | | |

+--------------+------------------+---------+-----------+-----------+-------------------+

Those genera marked * have since been found outside the group.

The authorities are thus indicated: (C)=Drake del Castillo; (H)=Horne;

(IK)=_Index Kewensis_ (S)=Seemann; (Sc)=Schimper; (So)=Solereder in

Engler’s _Nat. Pflanz. Fam._

The fact that several of them are fitted for dispersal by frugivorous

birds is very suggestive of the lack of means of transport in later

times. In the instance of Couthovia corynocarpa the drupes are known to

be the food of fruit-pigeons at the present time (Seemann), whilst this

is also true of Oncocarpus vitiensis, though this genus has since been

found in New Guinea. Since, as will be pointed out in a later chapter,

birds must still be fairly active in carrying seeds to Fiji from regions

westward, it would seem that genera only become peculiar to Fiji when

they fail at their source, and it is indeed doubtful whether any of the

Fijian peculiar genera are home productions. One may instance in this

connection the genus Pimia, the fruits of which are especially well

suited for attachment to a bird’s plumage, yet it is only known from

Fiji.

It should be here observed that no peculiar generic types have been

recorded from the adjacent Tongan Group, and scarcely any from Samoa.

Except perhaps with the Palmaceæ, no peculiar genera seem to be

mentioned in Dr. Reinecke’s memoir on Samoa.

_Summary._

(1) The Lobeliaceæ, like the Compositæ, take a prominent place in the

early Pacific flora, being represented, more particularly in Hawaii but

also in the East Polynesian or Tahitian region, by endemic genera of

tall shrubby and tree-like species.

(2) Tree-Lobelias occur in other parts of the world, as in South America

and tropical Africa; but it is especially on the higher slopes of the

mountains of Equatorial Africa that they attain a development comparable

with that of Hawaii.

(3) In Hawaii the Tree-Lobelias are most characteristic of the middle

forest-zone (3,000-6,000 feet), where the temperature is mild, the

rainfall heavy, and the atmosphere laden with humidity.

(4) The affinities of these endemic genera of the Lobeliaceæ are mainly

American; but their generic distinctions have been both exaggerated and

disguised by redundant growth.

(5) From the distribution of the genera and species within the Hawaiian

Group it is evident that, as with the early Compositæ, the original

Lobeliaceous immigrants were not all contemporaneous arrivals. Some of

the genera are on the point of extinction, whilst others are in their

prime.

(6) The absence of the Lobeliaceæ from the groups of the Fijian area

(Fiji, Tonga, Samoa) is probably to be connected, as in the case of the

absence of the early Compositæ, with the circumstance that the general

distribution of these two orders over the tropical Pacific occurred

during the Tertiary submergence of these archipelagoes.

(7) These endemic genera of the Lobeliaceæ possess the same facilities

for dispersal that are owned by other genera with minute seeds, such as

Cyrtandra, &c., that are dispersed over the Pacific; but in the case of

the Lobeliaceæ the agencies of dispersal have been for ages suspended.

(8) This suspension is to be associated with the diverting of the main

stream of migration from its source in America, during the early age of

the Lobeliaceæ and Compositæ, to a source on the Asiatic side of the

Pacific.

(9) The Hawaiian endemic genera other than those of the Compositæ and

Lobeliaceæ arrange themselves in two groups—an earlier group containing

highly differentiated Caryophyllaceæ and Labiatæ, and belonging to the

age of the Compositæ and Lobeliaceæ; and a later group, characterised by

Rubiaceæ and Araliaceæ, which marks the close of the first era, as well

as the change in the main source of the plants from America to the Old

World, the beginning of the Hawaiian forests, the appearance of the

Rubiaceous drupe, and the first active intervention of frugivorous

birds.

(10) Though there are no “difficult” or “impossible” fruits (fruits, the

dispersal of which is not easy to explain) amongst the forty and odd

endemic genera of Hawaii and Tahiti, it is noteworthy that in some cases

the fruits are seemingly little fitted for dispersal now, and that this

deterioration in capacity for dispersal is to be frequently associated

with more or less failure of the inter-island dispersal in the case of

Hawaii.

(11) The interest associated with the Hawaiian endemic genera fails to

attach itself to those of Fiji, where genera only seem to have become

peculiar because they have failed at their sources in the regions to the

west. The endemic genera of the Compositæ and Lobeliaceæ are here

lacking, and this is true also of the neighbouring Samoan and Tongan

Groups, it being held that the age of the general dispersion of these

orders over the Pacific corresponded with the Tertiary submergence of

the archipelagoes of the Western Pacific. Those of Fiji, which do not

amount to ten in number, belong to nearly as many orders and present a

motley collection such as one might look for in a group much less

isolated than Hawaii and exposed to wave after wave of migration from

the west.

CHAPTER XXIII

THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS

THE MOUNTAIN-FLORAS OF THE PACIFIC ISLANDS AS ILLUSTRATED BY THE

NON-ENDEMIC GENERA

The mountain-flora of Hawaii.—A third of it derived from high southern

latitudes.—An American element.—Compared with Tahiti and

Fiji.—Capacities for dispersal of the genera possessing only endemic

species.—Acæna, Lagenophora, Plantago, Artemisia, Silene, Vaccinium,

&c.—Capacities for dispersal of the genera possessing non-endemic

species.—Cyathodes, Santalum, Carex, Rhynchospora.—Fragaria chilensis,

Drosera longifolia, Nertera depressa, Luzula campestris.—Summary.

THE AGE OF THE ENDEMIC GENERA OF FLOWERING PLANTS.

WE are now entering an era distinguished from the preceding age of the

endemic genera, the age chiefly of the Compositæ and Lobeliaceæ, by the

fact that the extreme isolation that followed that era no longer

prevails. In a sense these island-floras are in touch again with the

world around, though the main stream of plant-migration now comes from

the south and from the west. Yet in a large number of cases, the amount

varying greatly in the different groups, it is evident that this stream

has not flowed continuously to the present day. The agencies of

dispersal are often no longer active; but the period of inactivity has

not been sufficiently prolonged to produce generic distinction, and the

differentiating energy has been restricted to the development of new

species.

Yet within these limits the development of new forms, as indicated in

Table B on p. 233, has often been very great. Thus, nearly half the

Hawaiian genera that are non-endemic are composed entirely of species

not found outside the group; and in this sense they may be regarded as

cut off from the regions around. In Fiji and Tahiti only about a fourth

are in this manner isolated, the agencies of dispersal being still

effective with the majority of the genera. It is apparent, therefore,

that the same question concerning the cause of the failure of the means

of dispersal presents itself in this era as in the last, and most

markedly in the instance of Hawaii.

The simplest and quickest plan for bringing into relief the prominent

features of this age is first to regard the genera from the standpoint

of the elevation of their stations. We have before remarked that in the

occurrence of extensive regions of great altitude the Hawaiian Islands

differ conspicuously from the groups of Tahiti and Fiji (and I may add

Samoa); and that they present conditions for the development of a

temperate mountain-flora that are not found at all in Fiji and are

barely represented in Tahiti. That the Hawaiian flora responds to this

contrast between the elevations of the three groups is well established;

and I will now proceed to refer more in detail to the subject.

THE MOUNTAIN-FLORAS OF THE PACIFIC ISLANDS.

In the Hawaiian Islands there are at least 37 or 38 genera, making up

about 19 or 20 per cent. of those belonging to this era, that may be

designated mountain genera, nearly all of them being characterised as

appertaining exclusively or in the main to temperate regions, or as

frequenting mountain-tops in tropical latitudes. In Tahiti there are

only 7 or 8 of such genera, about 4 per cent. of the total for the era.

In Fiji, excluding the Conifers, there are only 4 or 5, or not 2 per

cent. of the whole. In Samoa, which may be included in the Fijian area,

there are 3, or about 2 per cent. of the total. These are results which

we might have expected from the varying altitudes of these groups, as

described in Chapter XIX.

Few things give more pleasure to the botanist than his recognition in

some remote locality of plants long familiar to him in other regions.

This will often be his lot on the mountain summits of Hawaii. If he has

been a mountain-climber in many countries, he will there notice again

the genera Artemisia, Geranium, Plantago, Ranunculus, Rubus, Sanicula,

Vaccinium, and others that he has met perhaps either in the Rocky

Mountains or in the Andes or in Equatorial Africa or in the Himalayas.

If fresh from Chile he will find on these heights the familiar Gunnera

and the Chilian Strawberry (Fragaria chilensis). If he has been in New

Zealand and in the islands of the Southern Ocean he will find old

friends in the genera Acæna and Coprosma. He may handle once again

plants like Nertera depressa, that he gathered on Tristan da Cunha; and

on the boggy summits of some of the mountains he will find the

ubiquitous Sun-dew (Drosera longifolia).

Within the limited area occupied by the peaks of Tahiti he will find

genera like Astelia and Coprosma that are at home in New Zealand or in

Antarctic America, and may even find, as in the cases of Coriaria

ruscifolia and Nertera depressa, the identical species that are at home

in those distant regions. Even on the summit of Rarotonga he will gather

a species of Vaccinium. In Fiji, here and there on some isolated

mountain-top he may come upon a remnant of this Antarctic flora, such as

a solitary species of Coprosma or Lagenophora, that will carry him back

for a moment to high southern latitudes; and in the highlands of Savaii,

in the neighbouring Samoan Group, he will find again Nertera depressa

and a species of Vaccinium. But that which will interest him most in

Fiji will be the tall conifers of the genera Dammara, Podocarpus, and

Dacrydium, which will bring to him memories perhaps of New Zealand and

southern Chile, of South Africa, and of the mountain-woods of Java and

of Southern Japan.

Yet the influence of isolation has been at work amongst the

mountain-plants of all these groups. The agencies that have dispersed

over the tropical Pacific plants from the cold latitudes of the southern

hemisphere, and those that have borne the seeds of Plantago, Sanicula,

and Vaccinium from mountain-top to mountain-top, even though it be to a

peak in mid-ocean, are to a great extent inactive now.

THE MOUNTAIN-FLORA OF HAWAII AS ILLUSTRATED BY THE NON-ENDEMIC GENERA.

Let us look in the first place at Hawaii, where the breaking off of

communication with the outside world is especially pronounced. Here, all

the species of two-thirds or more of the mountain-genera are confined to

that group. Only in a relatively small number of cases are the species

in touch with the regions outside. The mystery of disconnection that is

so evident in the instance of the peculiar or endemic mountain-genera of

the Compositæ and Lobeliaceæ and other orders is here again presented to

us, and once more in the upland regions 4,000 to 10,000 feet above the

sea. We will now endeavour to discover from an examination of the

present distribution of the isolated mountain-genera (those non-endemic

genera possessing only peculiar species) along what tracks they arrived

at the Hawaiian uplands, tracks, as indicated by the local distribution

of the species, that have been more or less abandoned since.

_The Mountain Genera with only Endemic Species._—By referring to the

Table on the following page it will be observed that nearly a third of

these mountain genera have now their principal homes in the high

latitudes of the southern hemisphere. They are components of what

Forster and Hooker have termed the “Antarctic” flora, a collection of

plants that range round the globe in high southern latitudes, namely,

over Fuegia, New Zealand, southern Australia, South Africa, and the

islands of the Southern Ocean, the “Antarctic” islands, as they have

been termed. These genera are Acæna, Gunnera, Coprosma, Lagenophora,

Astelia, Oreobolus, and Uncinia. (It is necessary to observe that I am

entirely indebted to the Introduction to the _Botany of the “Challenger”

Expedition_ for my information on the “Antarctic” flora.)

We are thus led to expect that some of the other mountain genera may

have been similarly derived from cool southern latitudes, even though

they may be scarcely included in the “Antarctic” flora. This is very

probably true of Myoporum and Exocarpus, two genera that are chiefly

centred in Australia. A species of Sophora (S. tetraptera) is now one of

the most widely dispersed of the plants of high southern latitudes, a

circumstance which at all events explains the capacity for transport

that the ancestor of the Hawaiian “Mamani” (S. chrysophylla) must have

originally possessed (see Chapter XV.). Kinship between the Hawaiian

species and southern forms has been found in the case of a few of the

widely ranging genera here represented. Thus Decaisne placed Plantago

princeps next to P. fernandeziana of Juan Fernandez; whilst according to

Hillebrand, Plantago pachyphylla resembles P. aucklandica from the

Auckland Islands. These resemblances are consistently associated with

the respective range in altitude of the Hawaiian plants, since Plantago

princeps occurs usually between 2,000 and 4,000 feet, and P. pachyphylla

between 6,000 and 8,000 feet, the species of greatest elevation being

related with the species of highest latitude. It is thus seen that these

endemic mountain genera with peculiar species have very evident

affinities with the plants of extra-tropical southern latitudes, and

especially with the “Antarctic” flora. This affinity will also be found,

as will subsequently be noticed, in the case of genera like Cyathodes

and Nertera, where there is still a specific connection with the outside

world.

THE MOUNTAIN-FLORA OF HAWAII, AS REPRESENTED BY THE NON-ENDEMIC

GENERA (Compiled from Hillebrand’s Flora).

+----------------+------------+---------------+--------------+------------+

| | Usual |---------------|--------------+ |

| | | | | | flora. | | | |All | |

| | | | | | |New | | | | | |

+----------------+------------+-+-+-+-+-------+-+-+-+--------+------------+

| | | | | | | | | | | | |

| WITH ALL SPECIES ENDEMIC. |

| | | | | | | | | | | | |

|Ranunculus (2) |6,000- 7,000|+| | | | |+| | | |Achene. |

|Viola (5) |2,000- 6,000|+| | | | |+| | | |Capsule. |

|Silene (4) |2,000- 9,000|+| | | | |+| | | |Capsule. |

|Geranium (6) |5,000-10,000|+| | | | |+| | | |Carpels. |

|Vicia (1) |7,000- 8,000|+| | | | |+| | | |Pod. |

|Sophora (1) |5,000-10,000|+| | | | | | | | + |Pod. |

|Rubus (3) |4,000- 7,000|+| | | | | |+| | |Berry. |

|Acæna (1) |5,000- 6,000| | | |+| |+| | | |Spinose |

|Gunnera (1) |3,000- 6,000| | | |+| |+| | | |Drupe. |

|Sanicula (1) |6,000- 8,000| | |+| | | | | | + |Prickly |

|Coprosma (9) |3,000- 9,000| | | | | + | | | | + |Drupe. |

|Lagenophora (1) | 6,000- | | | |+| |+| | | |Viscid |

|Artemisia (2) |4,000- 8,000|+| | | | |+| | | |Achene. |

|Lobelia (5) |2,000- 6,000|+| | | | |+| | | |Capsule. |

|Vaccinium (2) |3,000- 8,000|+| | | | | | | | + |Berry. |

|Plantago (2) |2,000- 8,000|+| | | | |+| | | |Capsule. |

|Exocarpus (2) |3,000- 6,000| | | | | + |+| | | |Fleshy nut. |

|Sisyrinchium (1)|4,000- 7,000| | |+| | |+| | | |Capsule. |

|Astelia (2) |2,000- 6,000| | |+| | | | | | + |Berry. |

|Oreobolus (1) | 6,000 | | |+| | |+| | | |Toothed |

|Uncinia (1) |3,000- 5,000| | | |+| |+| | | |Awned |

|Agrostis (3) |4,000- 6,000|+| | | | |+| | | |Awned grain.|

|Deschampsia (3) |3,000- 6,000|+| | | | |+| | | |Awned grain.|

|Trisetum (1) |3,000- 5,000|+| | | | |+| | | |Awned grain.|

|Poa (2) | |+| | | | |+| | | |Grain. |

| | | | | | | | | | | | |

| WITH ENDEMIC AND NON-ENDEMIC SPECIES. |

| | | | | | | | | | | | |

|Cyathodes (2) |2,000-10,000| | | | | + | | |+| |Drupe. |

|Carex (5) |2,000- 7,000|+| | | | | |+| | |Nutlet. |

| | | | | | | | | | | | |

| WITH NO ENDEMIC SPECIES. |

| | | | | | | | | | | | |

| chilensis |4,000- 6,000| | |+| | |+| | | |Fleshy. |

| longifolia | 4,000 |+| | | | |+| | | |Capsule. |

|Nertera depressa|2,500- 5,000| | | |+| | | | | + |Drupe. |

| campestris |3,000-10,000|+| | | | | | |+| |Capsule. |

+----------------+------------+-+-+-+-+-------+-+-+-+--------+------------+

It is evident that in one or two cases the connection between the

representatives of the “Antarctic” genera on the Hawaiian uplands and

those of high southern latitudes has only been recently broken off. Thus

with reference to the Hawaiian species of the Cyperaceous genus,

Uncinia, it may be observed that although Hillebrand regards it as a

distinct species, Hemsley (_Intr. Bot. Chall. Exped._, p. 31) remarks

that it is very near if not the same as a New Zealand species, an

affinity very significant of the source of the mountain plants of this

group that are derived from these southern latitudes.

The next component to be recognised in these Hawaiian mountain genera

with peculiar species is a small special American element; and in this

connection Sanicula and Sisyrinchium may be especially mentioned. The

first is mainly North American, and particularly Californian; but there

are two solitary species found on the continents and in oceanic islands

such as the Azores. The continental species, Sanicula europæa, occurs

not only in Europe and Central Asia, but in South Africa, and at high

elevations on the mountains of Equatorial Africa and of Madagascar. It

is not, however, with this widely ranging species that Sanicula

sandwicensis is related, but with S. menziesii, a species from

California and Oregon (Hillebrand). Sisyrinchium is confined to

temperate and tropical America; but a singular and suggestive outlier of

the genus (S. bermudiana) is found in Bermuda.

The mountain genera that are distributed on both sides of the Pacific

constitute about three-fifths of the total. So far as my scanty data

show, they seem to have reached Hawaii from the four quarters of the

compass. The probable southerly origin of Plantago has been already

indicated. Hillebrand notes the great resemblance between Lobelia

gaudichaudii and an undescribed species from the Liukiu Islands, lying

on the west side of the Pacific. It is likely, also, that the genus

Ranunculus reached Hawaii from the west, since one of the species, R.

mauiensis, resembles R. repens of the Old World (Hillebrand); whilst the

other, R. hawaiiensis, comes near R. sericeus of Mauritius (Drake del

Castillo). On the other hand, the genus Rubus may hail from an American

source, since, in the opinion of Gray, Rubus hawaiiensis, one of the

mountain raspberries, finds its nearest relative in R. spectabilis from

the north-west coast of America; and there are reasons for believing, as

will subsequently be shown, that the genus Artemisia has an American

source. It is also probable that some of these genera have reached

Hawaii from the north, since it is likely, as pointed out in a later

page, that the Carices of the Hawaiian uplands came originally from

north-eastern Asia.

In the previous paragraphs the mountain genera have been considered with

especial reference to their distribution and source beyond the confines

of the Pacific. If we now briefly discuss them from the standpoint of

their distribution within the Pacific, or rather as concerning their

presence or absence in the Fijian and Tahitian groups, we shall see that

to a large extent Hawaii has received its mountain genera of this era

independently of the other Pacific groups.

Mountain genera possessing only peculiar species, in Hawaii only 20

Mountain genera possessing only peculiar species, in Hawaii and Fiji 2

Mountain genera possessing only peculiar species, in Hawaii and Tahiti 0

Mountain genera possessing only peculiar species, in all three groups 4

—

It is here shown that three-fourths of the genera of the Hawaiian

mountains in this era are not found either in Fiji or Tahiti. This, as

before pointed out, is mainly to be attributed to the greater elevation

of the Hawaiian Islands. Had there been an island 13,000 to 14,000 feet

in height in Fiji, we cannot think that any such contrast in the floras

would have existed. The temperate genera of the Hawaiian uplands would

have been largely represented in the Fijian flora. Yet although we do

not find such genera as Ranunculus, Geranium, Sanicula, Uncinia, &c., in

Fiji and Tahiti, a small number of the Hawaiian mountain genera have

obtained a scanty footing. This is what we might have expected. Thus,

Lagenophora has been found on the mountains of Vanua Levu, and Vaccinium

in Tahiti and Rarotonga; whilst Coprosma and Astelia occur on the tops

of some of the mountains in both regions. In Fiji their distribution

seems sporadic, as shown not in Lagenophora alone, but also by Astelia,

which has been found only on the summit of Kandavu.

_The Capacities for Dispersal of the Hawaiian Non-endemic Mountain

Genera possessing only Peculiar Species._—As shown in the Table, seven,

or 27 per cent., of these genera have fleshy fruits that would attract

frugivorous birds. In three cases (Gunnera, Coprosma, Myoporum) they are

drupes, in three others (Rubus, Vaccinium, Astelia) they are berries,

and in one (Exocarpus) there is a nut with a fleshy perigone. It is

particularly interesting to notice that frugivorous birds, and I include

here granivorous birds that are known to be frugivorous at times, could

have transported seeds of the “Antarctic” flora to this group. We can

observe the process in operation in our own time within the limits of

the group. It has been long known, and we find it referred to in the

pages of Hillebrand’s work, that the wild mountain-goose (Bernicla

sandwicensis) feeds upon the fruits of Coprosma ernodeoides, and of

Vaccinium reticulatum, the famous “ohelo.” The fruits of the first are

known to the natives as “kukai neenee” (droppings of geese), and the

hard stones or pyrenes are very well suited for withstanding the risks

of the digestive process. I found a number of these pyrenes in the

stomach of a mountain-goose shot by my companion, Dr. Krämer, high up

the slopes of Mauna Loa.

According to Mr. Perkins, Chloridops kona, a big Hawaiian finch, feeds

on the fruits of the bastard sandal-tree (Myoporum sandwicense). There

are no “impossible fruits” among the mountain genera of Hawaii, that is

to say, fruits so large that bird agency must be excluded. All of them

are practicable in point of size. Thus amongst the largest, the “stones”

of Gunnera would not exceed 1/5 of an inch (5 mm.), and those of

Myoporum scarcely 1/4 of an inch (6 mm.); whilst the nuts of Exocarpus

range in the Hawaiian species from 3/10 to 6/10 of an inch (7-15 mm.),

and the beans of Sophora chrysophylla do not at the most exceed 1/4 of

an inch (6 mm.).

The principal feature, however, which these mountain genera exhibit from

the point of view of their dispersal is the number of plants possessing

seeds or fruits capable of adhering to plumage. Half of these genera are

thus characterised. Of these Sanicula and Acæna represent the ordinary

hooked fruits; whilst the fruits of the Grasses and Sedges, Agrostis,

Deschampsia, Trisetum, Poa, Oreobolus, and Uncinia, are enabled by means

of their awns or of their serrated beaks to attach themselves to

plumage, and the same may be said of the carpels of Geranium. The fruits

of Lagenophora and the seeds of Plantago display the capacity of

adhesiveness by means of a gummy secretion.

One or two of these genera need further mention. I will first take

Acæna, which is spread all over the south temperate zone both on the

continents and on the islands. The Hawaiian species (A. exigua) forms

tussocky growths on the swampy summits of Mount Eeka in Maui, and in

Kauai, at an elevation of 6,000 feet above the sea. Numerous observers

refer to the probable mode of dispersal of the genus in the “Antarctic”

and neighbouring islands. Captain Carmichael, in the instance of Acæna

sanguisorbæ on Tristan da Cunha, observes that it overruns the low

ground. Its burr-like fruit, as he describes, “fixes itself on the

slightest touch into one’s clothes, and falling into a hundred pieces

covers one all over with an unseemly crust of prickly seeds not to be

got rid of without infinite labour” (_Trans. Linn. Soc._, xii. 483,

1818). Both Mr. Moseley (Wallace’s _Island Life_, p. 250) and Dr. Kidder

(_Bull. U.S. Nat. Mus._, 2) refer to the burrowing habits of the

Petrels, Puffins, and other sea-birds amongst the vegetation covering

the ground in Tristan da Cunha, Marion Island, Kerguelen, &c., in places

where Acæna, amongst other plants, thrives. Mr. Moseley remarks that the

fruits of this genus stick like burrs to feathers, and he looks to

sea-birds for the dispersal of this and similar plants over the ocean.

He especially notes that the Petrels and other seafowl burrow and breed

high up the mountain-slopes of tropical islands as in Tahiti, Viti Levu,

Hawaii, and Jamaica.... It should be noted in the case of the Hawaiian

endemic species that it has been found only on two mountain tops; and

that however active may be the dispersal of the genus in south temperate

latitudes now, the Hawaiian Islands lie outside the present area of

dispersal.

The next mountain genus I will specially refer to is Lagenophora, one of

the Compositæ. The solitary Hawaiian endemic species, L. mauiensis, is

restricted to the summit of Mount Eeka, in Maui. In the mountains of

Vanua Levu, Fiji, another peculiar species, L. pickeringii, has been

found; and there is a species, L. petiolata, in the Kermadec Islands

(Hooker, in _Journ. Linn. Soc._, i. 127); but the genus is chiefly

characteristic of Australia, New Zealand, and temperate South America,

one species occurring both in Fuegia and Tristan da Cunha. The genus has

no pappus; but Hooker in the case of the Kermadec species considered

that the “viscid fruit” favoured its dispersal; and this may probably be

true of the genus.

With regard to the capacity for dispersal of the seeds of Plantago, it

may be pointed out that the seeds of Plantago major, P. lanceolata, &c.,

become coated with a mucilaginous material when wetted. In 1892, when

experimenting on these plants, I found that the wetted seeds adhered

firmly to a feather, so that it could be blown about without their

becoming detached. Species of Plantago are so characteristic of the

“alpine” floras of the summits of lofty mountains in the tropics, as in

Java and many other regions, that the mode of dispersal has always been

a subject of curiosity. I cannot myself doubt that this is the

explanation of the occurrence of the representatives of the genus that

now thrive as endemic species on the higher slopes of the Hawaiian

mountains. This method of dispersal for Plantago is recognised by recent

writers on the subject of seed-dispersal. (In a paper in _Science

Gossip_ for September, 1894, I dealt with the “mucous adhesiveness” of

such seeds as a factor in dispersal. The subject had previously been

discussed by Kerner in one of the earlier volumes of his

_Pflanzenleben_; and I have summed up some of the results in Note 43 of

the present volume.) My readers can readily ascertain by a simple

experiment that a bird pecking the fruit-spikes in wet weather would

often carry away some of the sticky seeds in its plumage. Several years

ago, when I was endeavouring to examine the condition of these seeds in

the droppings of a canary, my efforts were defeated by the bird itself,

since, in spite of all my care, some seeds and capsules were always

carried by the bird on its feathers into the clean cage reserved for the

experiment.

The plants of these mountain genera possessing dry seeds or fruits

neither very large nor very minute and suitable for bird-food are

Ranunculus, Viola, Vicia, Sophora, Artemisia, Sisyrinchium, six in all,

or 24 per cent. of the total. On the probable method of transport of the

ancestors of these endemic species the following remarks may be made.

With regard to Ranunculus, some authors like C. M. Weed

(_Seed-Travellers_, p. 48, Boston, 1899) perceive in the curved or

hooked beaks of the achenes a means of attaching the fruit to plumage.

This no doubt applies to some species, and it is advocated by Ekstam for

some of the plants of the Nova Zembla flora. There are others to which

this explanation would not be applicable, and the achenes of the

Hawaiian species do not appear to be specially fitted for this mode of

transport. I have found the achenes of Ranunculus frequently in the

stomachs of birds in England, in partridges frequently, and in wild

ducks at times. Those of certain species that possess buoyancy are

common in the floating seed-drift of rivers, as of the Thames (_Journ.

Linn. Soc. Bot._, xxix. 333), and they would probably in this way be

often swallowed by waterfowl.

I have but few data directly relating to the dispersal of seeds of Viola

by birds. From the frequent occurrence of species in alpine floras, as

in the Caucasus, the Great Atlas, in the mountains of Equatorial Africa,

in Madagascar, &c., it may be inferred that birds transport the seeds

between the higher levels of many continental ranges in tropical regions

and to the mountain-slopes of neighbouring large islands. Viola

abyssinica, for instance, which occurs in Madagascar, is spread over the

elevated mountain ranges of tropical Africa. With regard to the five

Hawaiian species, it may be remarked that three of them are bog species

and two occur in dry situations. The first are most characteristic of

the mountains, one species occurring on the summit of Mount Eeka, 6,000

feet above the sea. Judging from the stations alone, at least two

species were originally introduced into the Hawaiian Group.

Viola seeds, as indicated by my experiments on the different British

species, including Viola palustris, are not buoyant, and there is no

possibility of the seeds being picked up by birds in floating drift.

There is, however, a possible means of dispersal in birds’ plumage by

means of the mucosity of the seeds of some species. Thus, although this

is not exhibited, as shown by my experiments, by Viola canina and V.

palustris, it is well displayed by the Field-Pansy (V. tricolor). I

found that the seeds of this species, after lying a little time in

water, were thickly covered with mucus, and that they adhered to a

feather, on drying, as firmly as if gummed. This did not, however, come

under my notice in the case of the seeds of one of the Hawaiian species,

V. chamissoniana, examined by me. One sometimes observes Viola canina in

England growing in places, as in the crevices and on the tops of old

walls, where its seeds could have only been carried by birds. In some

cases the propellent force of the seed ejected by the contracting valves

of the capsule would explain queer stations. In its power of

seed-expulsion, Viola chamissoniana, the common Hawaiian species, is

just as active as our British species.

With regard to the Leguminous genus Vicia we have the observation of

Focke on the dispersal of its seeds by pigeons, as described before on

page 150.

Sophora chrysophylla, the “Mamani” of the natives and one of the most

familiar of the trees of the Hawaiian mountains, is discussed at length

in Chapter XV., where the difficulty of supposing that its seeds could

be transported unharmed in a bird’s stomach half-way across the Pacific

is pointed out; and it is suggested that it was more probably derived

from a littoral species brought by the currents. However, the point is a

debatable one, and the seeds of the “Mamani” can scarcely be regarded as

“impossible” from the standpoint of dispersal.

With reference to the possibilities of dispersal of the achenes of

Artemisia, some very suggestive indications are to be obtained from a

paper by Mr. D. Douglas on the North American Tetraonidæ published in

the _Transactions of the Linnæan Society_ for 1833. The “Cock of the

Plains” (Tetrao urophasianus), as we here learn, makes its nest on the

ground under the shade of Artemisia bushes, and lives on the foliage and

fruits of these and other plants. This bird is plentiful in Columbia and

North California, and another allied species is mentioned which lives on

the same sort of food. Later authors refer to these and other birds of

the same family as living chiefly on the Sage-brush (Artemisia

tridentata), a plant prevailing over great regions of the plains as well

as on the slopes of the Sierra Nevada and of the Rocky Mountains.

According to Dr. Sernander (page 228), birds when feeding on the fruits

of Artemisia vulgaris in the district of Upsala scatter them about and

thus aid in its dispersal. Artemisia achenes, since they have neither

pappus nor other appendages, nor any special adhesiveness when wetted,

depend largely on their small size and light weight to aid them in

dispersal. (Those of A. absinthium measure a millimetre in length, or

1/25 of an inch, whilst those of A. vulgaris measure 1·8 mm., or 1/14 of

an inch.) Driven as we are to look to bird-dispersal for the means of

transport of Artemisia achenes, it is interesting to find a possible

source of the Hawaiian endemic species on the nearest American mainland,

even though it is some 2,000 miles away. It is assumed that they would

be ordinarily carried in adherent soil or entangled in the feathers, and

on rare occasions in the bird’s stomach.

The small seeds of Sisyrinchium possess no means of adherence to

plumage. They are crustaceous, and in cases where the stomach and

intestines of a bird are well filled with other food they are quite

capable of resisting injury. The solitary Hawaiian species has,

according to Hillebrand, a range in altitude from 3,500 to 7,000 feet. I

found this pretty herb most abundant on the “cattle-plains” of Hawaii

between 5,000 and 6,000 feet, where it is evidently in part dispersed by

the cattle and other animals. The seeds are very small, being about a

millimetre in size, and when dried nearly 100 go to a grain (0·65

decigramme). They might thus also be transported in mud on birds’ feet.

For the mode of dispersal of the minute seeds of Lobelia, the last of

the mountain genera to be specially noticed, I must refer the reader to

the remarks on this subject in Chapter XXII. They would probably be

carried in soil adhering to the legs or feet of a bird.

There are one or two interesting points relating to the temperate genus

Silene, which is represented on these mountains. The four Hawaiian

species show a great range in altitude. Thus, whilst S. struthioloides

finds its home in Hawaii and Maui at elevations of 5,000 to 9,000 feet,

another species (S. lanceolata) thrives equally at elevations of 5,000

or 6,000 feet on the central plateau of Hawaii and at heights only of

300 to 500 feet above the sea. Although I have not yet come upon any

direct reference to the mode of dispersal of the small seeds of this

genus, there is little doubt that their rough tuberculated surfaces

would favour their attachment to plumage. A very significant

observation, however, is made by Jens Holmboe in a paper on littoral

plants in the interior of Norway. He refers to the occurrence in no

small quantity of Silene maritima on the top of “Linnekleppen,” 331

metres high, one of the highest peaks of Smaalenene, and distant about

29 kilometres from the nearest coast (_Strandplanter i det indre af

Norge_, “Naturen,” Bergen, 1899). Sernander (p. 405), commenting on this

observation, remarks that since bare hill-tops are frequented by birds,

such an agency in this instance is not impossible.

I will conclude these remarks on the non-endemic Hawaiian mountain

genera possessing only peculiar species, with a few observations on the

genus Vaccinium in the Pacific. This genus is known to be distributed

over the northern hemisphere and to occur on the uplands of tropical

mountains, as, for instance, on the summits of the Java mountains and on

the high levels of the Equatorial Andes at altitudes even of 15,000 to

16,000 feet. There are apparently only some four or five species known

from the Pacific islands, from Hawaii, the Marquesas, Tahiti, Rarotonga,

Samoa, and the New Hebrides, and it would almost seem that these can be

reduced to one or two species. Although not yet recorded from Fiji, the

probability of the genus being represented on some of the mountains is

pointed out by Seemann. Of these Pacific forms a single species, V.

cereum, is spread over the East Polynesian region including the

Marquesas, Tahiti, and Rarotonga; and, according to Hillebrand, V.

reticulatum, one of the two endemic Hawaiian species, is nearly related

to it. Even the New Hebrides species (V. macgillivrayi) resembles it,

according to Seemann, in general appearance. That there has been a

single Pacific polymorphous species is, as shown below, not impossible;

but Reinecke, in describing in 1898 the Samoan species, V. antipodum,

was under the impression that it was the only species known from the

southern hemisphere, and says nothing of its affinity to other Pacific

plants.

A few words on the station and habit of Vaccinium in the Pacific islands

may be here of interest. In Hawaii there are, according to Hillebrand,

two species, a high-level form, V. reticulatum, occurring at elevations

of 4,000 to 8,000 feet, and a low-level form, V. penduliflorum, ranging

between 1,000 and 4,000 feet. I may, however, remark that the last

species occasionally came under my notice at elevations of 6,000 to

7,000 feet. This species exhibits much variation, and Gray, Wawra, and

other botanists have evidently not been always able to distinguish

between the two species in their varying forms. It is not only

distinguished from the high-level species by its lower station, but also

by its epiphytic habit, a circumstance that, as pointed out below, may

explain some of the differences, since such a habit is bound up with the

difference in station. It seems, therefore, safer to regard them as

station forms of one species which is closely allied to V. cereum, the

species of the South Pacific, an inference which, if well founded, would

make highly probable the view that there has been a single polymorphous

Pacific species.... In Tahiti, as we learn from Nadeaud, V. cereum

occurs on the mountain-tops at altitudes exceeding 800 metres (2,600

feet). In Rarotonga, according to Cheeseman, it is found on the summits

of most of the higher hills extending almost to the summit of the

island, 2,250 feet above the sea. The Samoan species, V. antipodum of

Reinecke, which that botanist considers as probably one with V. whitmei,

a Polynesian (Samoa?) species originally described by Baron F. von

Müller, grows in the central mountains of Savaii at an elevation of

1,500 metres (4,920 feet).

These Pacific species of Vaccinium, as on tropical mountains of the

continents, occasionally assume an epiphytic habit, and it is here, as

above observed, that lies one of the distinctions between the Hawaiian

species. V. penduliflorum, the low-level form, occurs typically in the

forests, where, according to Hillebrand, it grows on the trunks of old

trees. The trees, however, may be quite in their prime, and I have

observed it growing in the fork of the trunk of an Olapa tree

(Cheirodendron gaudichaudii). It is in this connection of significance

to notice that a variety found in open glades and on grassy slopes is

described by Hillebrand as terrestrial in habit. The other high-level

form, V. reticulatum, grows gregariously on open ground, and is

typically terrestrial in its habit. The Samoan species, as we learn from

Reinecke, grows on trees, as on the branches of Gardenia. The epiphytic

habit of species of Vaccinium is especially discussed by Schimper in the

case of plants growing on the Java mountains. He there shows

(_Plant-Geography_, i. 14) that species which are epiphytes in the

virgin forest become terrestrial plants in the treeless alpine region.

This interchange of station, which is exhibited by several other plants,

including orchids and ferns, is connected with their xerophilous

characteristics, and is given by Schimper as an example of the

interchange of physiologically dry habitats.

Of the mode of dispersal of Vaccinium by frugivorous birds, much has

been written and much will be familiar to my readers. The berries of V.

reticulatum are known to be the principal food of the Hawaiian

mountain-goose. But probably birds of the grouse family have been the

chief agents in distributing the genus over the continents. I have

frequently found the fruits in the stomachs of the Black Cock (Tetrao

tetrix), the Scotch Grouse (Lagopus scoticus), and the Capercailzie

(Tetrao urogallus); but the same story comes from all over the northern

hemisphere. The Willow Grouse (Lagopus albus), which travels round the

globe, is known to feed on them. Hesselman in Sweden and Ekstam in Nova

Zembla have especially investigated the dispersal of Vaccinium by Tetrao

tetrix and Lagopus (see Sernander, pp. 6, 226); and according to Mr.

Douglas and others the different species of Tetrao that frequent the

subalpine regions of the Rocky Mountains and the uplands of Columbia and

North California subsist on Vaccinium fruits. This family is not now

represented in the Hawaiian avifauna; but it is noteworthy, as indicated

by the differentiation of the Pacific species of Vaccinium, that

dispersal of the genus is there almost suspended except within the

region of Eastern Polynesia. It is probable that numerous other birds,

except the Hawaiian goose, aided the original dispersal.

_The Mountain Genera with both Endemic and Non-endemic Species._—I pass

on now to consider those Hawaiian mountain genera that possess species

some of which are confined to the group, whilst others occur in regions

outside the islands. They are not many, as may be seen from the table

before given, and but few of them are entirely restricted to the high

levels, a range in altitude that may be frequently associated with great

lateral extension of the genus over different latitudes. Here the agents

of dispersal have through some species in each genus preserved a

connection with the outer world, though it may be restricted to the

limits of the Pacific islands.

Cyathodes tameiameiæ, an Epacridaceous species found also in the uplands

of Tahiti, occurs, according to Hillebrand, on all the Hawaiian Islands,

from 1,800 feet up to the limit of vegetation 10,000 feet and over above

the sea. I found it, however, at even lower levels. On the Puna coast of

Hawaii, associated with Metrosideros polymorpha, Osteomeles

anthyllidifolia, and other inland plants, it descends on the surface of

ancient lava-flows to the coast wherever the bolder spurs reach the

sea-border. The other species, C. imbricata, is more exclusively

confined to the greater altitudes. It is endemic, and may possibly be a

station form of the other species.

The six species of Lysimachia are found at different elevations, one

near the sea-shore, others at altitudes of 2,000 to 3,000 feet, and

others again at elevations of 6,000 feet. Chenopodium sandwicheum occurs

at all elevations from near the coast to the high inland plains of

Hawaii and to the upper slopes of Mauna Kea, that is to say, up to

altitudes of 6,000 or 7,000 feet. Hillebrand observes that it is a low

decumbent plant at the coast, and may become arborescent with a height

of 12 to 15 feet in the upper forests of Mauna Kea.

The species of Santalum (sandal-wood trees) also display great vertical

range in these islands. Though S. freycinetianum, which is also a

Tahitian species, is most at home in the forests 2,000 to 4,000 feet

above the sea, it has, as Hillebrand informs us, a dwarfed form that

extends far up the mountain slopes of Mauna Loa and Hualalai to

elevations of 7,000 or 8,000 feet, and another dwarfed shrubby variety

that grows only near the sea-shore. Another species, S. haleakalæ,

occurs as a tall shrub on Haleakala at elevations of 8,000 to 10,000

feet. Among the sedges, most of those of the genera Carex and

Rhynchospora are found at altitudes of between 3,000 and 7,000 feet, and

two grasses of the genus Deyeuxia occur at elevations of 6,000 to 8,000

feet.

Amongst these Hawaiian mountain genera with both endemic and non-endemic

species there are no plants possessing fruits which from their size

could be with difficulty regarded as dispersed by birds. The mode of

dispersal of these plants is in some cases indeed not far to seek. Thus

in the stomach of an Hawaiian goose (Bernicla sandwicensis), shot by my

companion Dr. Krämer on the slopes of Mauna Loa, I found a number of the

“stones” of Cyathodes tameiameiæ, the plant being abundant in fruit in

the immediate vicinity. It is highly probable that the seeds of Santalum

have been carried over the Pacific by frugivorous birds. We learn from

Dr. Brandis that Santalum album in India is mainly spread through the

agency of birds (_Bot. Chall. Exped._, iii. 13). The drupes of the

Pacific species, S. freycinetianum, that occurs alike in Hawaii, the

Marquesas, and Tahiti (Drake del Castillo), measure about half an inch.

There can be little doubt that with this tree, as with the species of

Cyathodes above mentioned, which also links together Tahiti and Hawaii,

there has been up to recent times an interchange by means of frugivorous

birds between these two regions, some 2,000 miles apart.

The small seeds of the capsular fruits of Lysimachia could be

transported in birds’ plumage or in dried soil attached to their feet or

feathers. The seed-like fruits of Chenopodium were probably dispersed by

some granivorous bird, much as nowadays our partridges carry about in

their stomachs the similar fruits of Atriplex. The long-awned fruits of

Deyeuxia were, it is likely, transported in birds’ plumage, and

doubtless also those of Panicum; whilst the nutlets of Carex and

Rhynchospora might have been carried about in a similar fashion.

The distribution of the non-endemic species of these Hawaiian mountain

genera may perhaps aid us in determining the original source of the

genus as well as in confirming the conclusions formed concerning the

other mountain genera that only possess species restricted to the group.

Lysimachia, Chenopodium, Carex, Rhynchospora, Deyeuxia, and Panicum are

found in both the Old and New Worlds. Since Hillebrand remarks that one

of the six species of Lysimachia (L. spathulata) occurs in Japan and in

the Liukiu, Bonin, and Marianne groups, we have here a valuable

indication of the route followed by a genus that has not been recorded

from the oceanic groups of the South Pacific.

The capricious distribution of the genus Carex in the Pacific is

remarkable, and it is noticed by Hemsley in the Introduction to the

_Botany of the “Challenger” Expedition_. No species have been recorded

from Tahiti, the Marquesas, and Rarotonga, but three Fijian species are

mentioned by Hemsley, and there is another in Samoa. Of the five

Hawaiian species given by Hillebrand, two are endemic. Of the rest, C.

wahuensis (oahuensis), Meyer, occurs also in Korea and Japan, whilst C.

brunnea, Thunb., is found in Japan and Australia, and the third, C.

propinqua, Nees., occurs all round the border of the Pacific Ocean, from

Kamschatka through Alaska south to the Straits of Magellan. These three

species all possess a home in common in north-east Asia, and probably

there lies the source of the Hawaiian species of Carex—a conclusion

which would help to explain the irregular distribution of the genus

amongst the South Pacific groups.

The genus Rhynchospora occurs alike in the Hawaiian, Tahitian, and

Fijian islands; but the groups in the North and South Pacific seem to

have been independently supplied with the original species, since R.

aurea, a widely spread tropical species, ranging the South Pacific from

New Caledonia to Tahiti, has not been recorded from Hawaii. A connection

between Hawaii and the Australian region seems to be indicated by a

species of Deyeuxia (D. forsteri) that is found also in Easter Island,

Australia, and New Zealand, and by the presence of the Australian and

New Zealand genus Cyathodes in Hawaii, though the existence of a species

common to both Tahiti and Hawaii goes to show that the route followed by

the genus lay through Eastern Polynesia. It is also not unlikely that

the genus Santalum reached Hawaii through Eastern Polynesia, since two

forms found in Hawaii and Tahiti are closely allied, and are, in fact,

regarded by Drake del Castillo as the same species. The genus occurs in

tropical Asia, Australia, and New Zealand.

Looking at the indications above given, I should be inclined to think

that the genera Lysimachia and Carex reached the Hawaiian mountains from

temperate Asia or the islands off its Pacific coast, and that Cyathodes,

Santalum, and Deyeuxia hail from the Australian or New Zealand region by

way of Eastern Polynesia.

_The Mountain Genera possessing no Endemic Species._—The few remaining

mountain plants of Hawaii to be considered are solitary, widely ranging

species of genera that here possess no peculiar species. Such may be

regarded as belonging to the latest age of the indigenous plants. They

still keep up, or kept up until recently, the connection with the world

outside Hawaii, and among them one may name here Fragaria chilensis,

Drosera longifolia, Nertera depressa, and Luzula campestris.

Fragaria chilensis, the Chilian strawberry, flourishes at elevations of

between 4,000 and 6,000 feet on the Hawaiian mountains. Its fruits,

according to Hillebrand and other authors, are much appreciated by the

wild goose of the islands. This plant ranges in America from Chile north

to Alaska; and Drake del Castillo is doubtless on safe ground when he

assumes that a congener of this bird originally brought the species from

the nearest part of the American continent, namely from California

(_Remarques_, &c., p. 8). In this connection it should be remembered

that one of the endemic mountain-raspberries of Hawaii (Rubus

hawaiiensis) finds its nearest relative, according to Gray, in Rubus

spectabilis, a species from the north-west coast of America.

The species of Sun-dew, Drosera longifolia, hitherto found only on the

marshy tableland of Kauai at an elevation of 4,000 feet above the sea,

occurs both in Asia and North America. Its minute fusiform seeds are

very light in weight, and might readily become entangled in a bird’s

plumage, or they could be carried in adherent dried mud.

Luzula campestris, which grows on the high mountains of the Hawaiian

group from 3,000 feet upward, is also found in Tahiti. It is widely

distributed in cool latitudes, and there is no special indication of its

source. Its seeds are especially well suited for adhering to birds’

feathers. When experimenting on these seeds in 1893 I ascertained that

whether freshly gathered or kept for more than a year they became on

wetting coated with mucus, and adhered firmly to a feather on drying.

There are many ways in which the “sticky” seeds in wet weather might

fasten themselves to a bird’s plumage. The plant-materials might be

used, for instance, for making nests. The Sea Eagle (Aquila albicilla),

as we learn from Mr. Napier (_Lakes and Rivers_), uses materials derived

from Luzula sylvatica in the construction of its nest.

Nertera depressa, a creeping Rubiaceous plant, with red, fleshy drupes

containing two coriaceous pyrenes, is found in all the Hawaiian Islands

at elevations of 2,500 to 5,000 feet, and it grows on the mountains of

Tahiti at altitudes over 3,000 feet. The genus is widely diffused over

the southern hemisphere. This particular species is characteristic of

the Antarctic flora, being found all round the south temperate zone

(excepting South Africa) in New Zealand, Fuegia, the Falkland Islands,

and Tristan da Cunha, and extending up the Andes to Mexico, occurring

also on the summits of Malayan mountains at elevations of 9,000 to

10,500 feet above the sea, as on Pangerango in West Java (Schimper), and

on Kinabalu in North Borneo (Stapf). Captain Carmichael, who resided on

Tristan da Cunha in the early part of last century, states (_Trans.

Linn. Soc._, xii. 483) that its drupes are eaten by a species of thrush

and by a bunting. Professor Moseley, who visited the island in the

_Challenger_ many years after, remarks that its fruits are “the

favourite food of the remarkable endemic thrush, Nesocichla eremita,”

the bunting being Emberiza brasiliensis (_Bot. Chall. Exped._, ii. 141).

It would seem most likely that the Hawaiian Islands received this

representative of the Antarctic flora through the Tahitian Islands, as

in the case of the species of Cyathodes common to both these groups.

Looking at the indications of these four widely ranging plants, the

Chilian strawberry (Fragaria chilensis), the Sun-dew (Drosera

longifolia), Nertera depressa, and Luzula campestris, it may be inferred

that with the exception of Nertera they all reached Hawaii from either

the Asiatic or American sides of the North Pacific, the last route being

evident in the case of the strawberry. Nertera depressa was probably

derived from southern latitudes.

_Summary._

(1) The second era of the flowering plants of the Pacific islands is

indicated by the non-endemic genera. Here also the isolating influences

have been generally active, and the work of dispersal is in some regions

largely suspended. Thus in Hawaii nearly half the non-endemic genera

possess only species that are restricted to the group, whilst in Fiji

and Tahiti about a fourth are thus isolated.

(2) The contrast in the elevations of the islands of the Hawaiian,

Tahitian, and Fijian regions is reflected in the development of an

extensive mountain-flora in Hawaii, in its scanty development in Tahiti,

and, excluding the Fijian conifers, in a mere remnant in Fiji and Samoa.

(3) The influence of isolation has been very active in the Hawaiian

mountains, since about two-thirds of the genera contain only species

confined to the group, and are thus disconnected from the world outside.

(4) Amongst these disconnected Hawaiian mountain genera, Antarctic or

New Zealand genera, like Acæna, Gunnera, Coprosma, and Lagenophora,

constitute nearly a third. The American element, represented, for

instance, by Sanicula and Sisyrinchium, is small; whilst the genera

found on both sides of the Pacific form more than one-half of the total,

and include genera like Ranunculus, Viola, Rubus, Artemisia, Vaccinium,

and Plantago, that often represent the flora of the temperate zone on

the summits of tropical mountains. Three-fourths of these genera are not

found either in Fiji or in Tahiti.

(5) The proportion of the disconnected Hawaiian mountain genera

possessing seeds or seedvessels suited for dispersal in a bird’s plumage

is very large, quite half belonging to this category; whilst only about

a fourth have fruits that would be dispersed by frugivorous birds.

(6) The Hawaiian mountain genera that still remain in touch with the

external world through species found outside the islands whilst other

species are confined to the group, present a later stage in the

plant-stocking. Their widely ranging species, which would be dispersed

either by frugivorous birds, as with Santalum and Cyathodes, or in

birds’ plumage, as with Lysimachia, Carex, and Deyeuxia, seem to

indicate that the main lines of migration for these genera have been

from temperate Asia and from the Australian and New Zealand region, the

last by way of Eastern Polynesia.

(7) The latest stage of the Hawaiian mountain-flora is exemplified by

those genera that are only represented in the group by a solitary

widely-ranging species, such as Fragaria chilensis, Nertera depressa,

Drosera longifolia, and Luzula campestris. It is our own age; and birds

are shown to be actual agents in the dispersal of the two first-named

species and to be probable agents with the two other species. The two

last-named species probably reached Hawaii from one or other side of the

North Pacific; whilst Fragaria chilensis doubtless hails from the

adjacent part of the American continent, and Nertera depressa from high

southern latitudes by way of Tahiti.

CHAPTER XXIV

THE MOUNTAIN-FLORAS OF THE TAHITIAN AND FIJIAN REGIONS

The mountain-flora of the Tahitian region, as illustrated by the

non-endemic genera.—Derived chiefly from high southern

latitudes.—Weinmannia, Coprosma, Vaccinium, Astelia, Coriaria,

Cyathodes, Nertera depressa, Luzula campestris.—The mountain flora of

Rarotonga.—The mountain-flora of the Fijian region, as illustrated by

the non-endemic genera.—Weinmannia, Lagenophora, Coprosma, Astelia,

Vaccinium, Nertera depressa.—The Fijian Coniferæ.—Dammara, Podocarpus,

Dacrydium.—Not belonging to the present era of dispersal.—The age of

dispersal of the Coniferæ in the Pacific.—Earlier than the age of

Compositæ and Lobeliaceæ.—The first in the Mesozoic period.—The last

in the Tertiary period.—Summary.

THE MOUNTAIN-FLORA OF THE TAHITIAN REGION AS ILLUSTRATED BY THE

NON-ENDEMIC GENERA

THIS floral region of the Pacific corresponds with the limits of Eastern

Polynesia, and includes not only the Tahitian group proper, but also the

Cook, Austral, Paumotuan, and Marquesan groups. It is only, however, in

Tahiti, the peaks of which rise to over 7,000 feet above the sea, that

we should expect to find such a mountain-flora, since the islands of the

other groups are much lower, the highest of them in the Marquesan group

barely exceeding 4,000 feet. Yet even in Tahiti it is not possible to

speak of a mountain-flora in the sense that we attach to it in Hawaii.

The elevated area of its interior is, as described in Chapter XIX.,

relatively very small; whilst, as Drake del Castillo points out, the

conditions presented by the steep mountain-slopes rarely afford a hold

for trees of any size, ferns often predominating in the higher levels.

Still, we can observe the traces of such a flora, and it is in this

sense only that the term “mountain-genera” is used in relation with this

group.

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

Weinmannia, Saxifragaceæ, from New Zealand. }

Coprosma, Rubiaceæ, from New Zealand. }all species

Vaccinium, Vacciniaceæ, from the northern hemisphere. }endemic.

Astelia, Liliaceæ, from New Zealand. }

Coriaria, Coriariaceæ, from New Zealand }some

Cyathodes, Epacridaceæ, from New Zealand }species

}endemic

Nertera depressa, Rubiaceæ, a species of the Antarctic flora.

Luzula campestris, Juncaceæ, from the northern hemisphere.

The Tahitian non-endemic mountain-genera, though scanty in number, are

of considerable interest to the student of plant-dispersal. Among those

possessing only species that are confined to Eastern Polynesia, genera

that would be regarded as belonging to a past era of dispersal,

Weinmannia, Coprosma, Vaccinium, and Astelia may be mentioned.

Weinmannia, a Saxifragaceous genus of trees and shrubs, not represented

in Hawaii, but recorded from almost all the elevated oceanic groups of

the tropical South Pacific, as well as from the New Hebrides and New

Caledonia, has its home in South America, more particularly in the

Andes, and also occurs in New Zealand, Tasmania, and the Mascarene

Islands. One can scarcely doubt that, as in the case of Coprosma, the

Pacific Islands derived their species originally from high southern

latitudes, as from New Zealand, the absence of the genus from Hawaii

negativing an American origin. Of the two Tahitian species, one is

peculiar to Tahiti, whilst the other, W. parviflora, which is

conspicuous on the mountain-crests at elevations of 3,000 feet and over,

occurs also in the Marquesas. Another species grows in abundance in the

interior of Rarotonga. Samoa possesses two species, one of which, W.

affinis, occurs in Fiji, and the other, W. samoensis, which frequents

the mountains at elevations of 1,500 to 3,300 feet, is seemingly

endemic. Fiji possesses four or five species of Weinmannia occurring at

all altitudes up to 2,000 feet, of which some are evidently peculiar.

The capsular fruits of this genus contain hairy seeds that would

probably become entangled in a bird’s plumage. Dispersal by birds is

distinctedly indicated in the curious observation of Dr. Reinecke in the

case of the Samoan peculiar species. The seeds, he says, appear to

germinate by preference on the bark of other trees, young plants growing

epiphytically being of frequent occurrence.

There is some evidence that the species of Weinmannia, about ten in all,

found in the tropical islands of the open Pacific are derived from one

or two polymorphous species. As we learn from Mr. Cheeseman, the

Rarotongan species, W. rarotongensis, has considerable affinity to

several closely allied Polynesian species, and its nearest allies are a

Fijian and Samoan species, W. vitiensis and W. samoensis. Possibly, he

remarks, fuller materials may lead to the union of several of these

forms under one species.

The interesting New Zealand genus Coprosma, which we have noticed in

Hawaii, occurs also in the Tahitian region and Fiji; and it will be

further discussed under the last-named locality. The genus Vaccinium has

been previously dealt with in Chapter XXIII.

The Liliaceous genus Astelia may be considered as representing, like

Coprosma, the Antarctic or New Zealand flora in the higher levels

(usually) of the islands of the tropical Pacific, where it grows both on

trees and on the ground. The genus, according to Hemsley, is chiefly at

home in New Zealand, but is also found in Fuegia and in South-east

Australia. It is represented in Hawaii, Tahiti, Samoa, and Fiji. In

Hawaii there are two peculiar species ranging between 2,000 to 6,000

feet in elevation. The solitary Tahitian species, A. nadeaudi, is found

in the central mountains of Tahiti, reaching to the crests of Mount

Aorai, which attains a height of 6,700 feet. Fiji and Samoa possess a

species in common, A. montana, which is only recorded by Seemann, from

the summit of Kandavu, 2,750 feet above the sea; whilst in Samoa it

frequents, according to Reinecke, moist coast districts. The fruits of

Astelia are berries with crustaceous seeds that would be dispersed by

frugivorous birds.

Amongst the Tahitian mountain-genera that possess species ranging far

beyond this region as well as species confined to the group may be

mentioned Coriaria and Cyathodes. It is to their non-endemic species

that we look for further clues as to the general lines of migration by

which the mountain-genera that only possess peculiar species reached

this group. The evidence afforded by Coriaria is of some importance. The

genus has not been recorded from Hawaii, and, so far as the collections

of Seemann and Home show, not from Fiji. It is found in the

Mediterranean region, the Himalayas, Japan, New Zealand, and Antarctic

America, including Chile; and there are two particular species, C.

ruscifolia and C. thymifolia, that occur in both cases in New Zealand

and the adjacent islands and in South America (Introd. _Chall. Bot._ p.

53). The first of these, which is very common in Chile, exists also in

Tahiti on the crest of Aorai, 6,700 feet above the sea. Drake del

Castillo also describes a peculiar Tahitian species, C. vescoi, of which

the altitude is not given. Here one is in doubt whether Tahiti derived

its wide-ranging species from New Zealand or from Chile; but in the New

Zealand home of Coprosma, another Tahitian mountain-genus, we are

afforded the clue. The fruits of Coriaria possess fleshy cocci that

attract birds, though it would seem that the seeds of plants of this

genus are poisonous for man. Among the numerous fruits that form the

diet of the New Zealand fruit-pigeon (Carpophaga novæ zealandiæ) are

included, as we learn from Sir W. Buller in his _Birds of New Zealand_,

those of the “tupakihi” or “tutu” shrub, which Kirk identifies with C.

ruscifolia, the species that also occurs on the summit of Tahiti.

The Australian and New Zealand genus Cyathodes (Epacridaceæ) has been

already noticed in the case of Hawaii (page 282). The two Tahitian

species occur on the elevated mountain-ridges forming the summits of

Tahiti, one of them, C. tameiameiæ, occurring also in Hawaii, and the

other, C. pomaræ, being restricted to the group. I have shown that the

fruits are dispersed by frugivorous birds, and I can only include the

genus as another example of the representation of the New Zealand flora

in Tahiti.... There remain of these so-called Tahitian mountain-genera

the Antarctic Nertera and the north-temperate Luzula, each represented

by a solitary widely ranging species, N. depressa and L. campestris,

which I have fully discussed under Hawaii (Chapter XXIII), in which

group they also occur.

When we look at the evidence of origin supplied by the four Tahitian

mountain-genera possessing species that are found outside the group,

namely Coriaria, Cyathodes, Nertera, and Luzula, we find that the first

three hail from high southern latitudes, and more especially from New

Zealand; and when with this clue in our hands we take up the four genera

Weinmannia, Coprosma, Vaccinium, and Astelia, possessing only species

restricted to the Tahitian region, we find that all but the third-named

genus hail also from the south. It would thus appear that the element of

the Antarctic flora is much more evident in the Tahitian mountain-genera

than with those of Hawaii. In the Hawaiian mountain-flora, excluding, of

course, the endemic genera, it includes about a fourth of the

mountain-genera, which number about thirty-eight or forty in all; whilst

in the Tahitian mountain-flora it comprises six out of the eight genera.

It may, indeed, be said that the resemblance between the mountain-genera

of Hawaii and Tahiti is mainly restricted to genera that are found in

high southern latitudes, namely, Nertera, Coprosma, Cyathodes, and

Astelia, the only other genera linking the mountain-floras of both

groups together being Vaccinium and Luzula, which probably hail from

high northern latitudes. The agency of the frugivorous bird is plainly

marked in the case of five out of the six genera that connect the

cloud-capped peaks of Tahiti and Hawaii. In two of these genera,

Cyathodes and Nertera, the same species occurs in both archipelagoes.

_The Mountain-flora of Rarotonga._—A word may here be said on the

representation of these mountain-genera in Rarotonga, a small island

2,250 feet in height and about eight miles in length, which is, however,

the most important island of the Cook group. The recent important

explorations of Mr. Cheeseman show that its flora is essentially

Tahitian in character. As in Tahiti, the early age of the Compositæ and

Lobeliaceæ is well represented in the high levels by peculiar species of

Fitchia and Sclerotheca which are discussed in Chapters XXI and XXII. On

account, however, of its relatively low altitude and its small size, we

could not expect any extensive representation of the eight non-endemic

mountain-genera of Tahiti. Yet three of these occur, a Tahitian species

of Vaccinium (page 281) growing on its summits, whilst peculiar species

of Weinmannia (page 290) and Coprosma (page 295) are found in its

interior. The prevailing condition of many of the genera growing in the

higher levels is one of isolation, since other genera, like Pittosporum

and Elæocarpus, only possess peculiar species; but seeing that in

several cases the species are closely allied to others found in the

Western Pacific, as in Samoa, Fiji, and the Kermadec group, it is

apparent that the period of isolation has not long commenced.

THE MOUNTAIN-FLORA OF THE FIJIAN REGION.

Weinmannia, Saxifragaceæ, Fiji and Samoa. } Derived from

Lagenophora, Compositæ, Fiji. } New Zealand or

Coprosma, Rubiaceæ, Fiji. } from the

Astelia, Liliaceæ, Fiji and Samoa. } Antarctic flora.

Vaccinium, Vacciniaceæ, Samoa, from the northern hemisphere.

Nertera depressa, Rubiaceæ, Samoa, from the Antarctic flora.

Dammara, Coniferæ, Fiji. }Not as a rule belonging

Podocarpus, Coniferæ, Fiji and Tonga. }to the present age

Dacrydium, Coniferæ, Fiji. }of dispersal

But little can be said of the mountain-flora of Fiji, since on account

of the relatively low elevation of the islands there are but few special

mountain-genera; and as a rule we find only here and there a solitary

species on some isolated peak that recalls the upland flora of the

Hawaiian mountains. “None of the mountains of Fiji,” remarks Horne (page

60), “are high enough for an alpine flora to exist. Many of the plants

found on the tops of the mountains are also found near the level of the

sea. On the other hand sea-level plants may also be found on the tops of

the hills.”

Fiji lacks the endemic genera of Compositæ and of Lobeliaceæ that often

give a character to the mountain-floras of the Hawaiian and Tahitian

regions, though, as remarked in Chapters XXI and XXII., their absence

involves something more than a question of station. We find, however,

four genera of the Antarctic or New Zealand flora, Weinmannia,

Lagenophora, Coprosma, and Astelia. The first-named genus possesses four

or five species ranging up to 2,000 feet, some of which are endemic, and

it has been already discussed in this chapter. The United States

Exploring Expedition found a single species of Lagenophora (L.

pickeringii) on the mountains of the Mathuata coast of Vanua Levu, and

no other species seems to have since been found. The subject is dealt

with in Chapter XXIII in the case of Hawaii, but it may be here observed

that there is an Hawaiian mountain species, and that the route followed

by the ancestor of the Fijian species from the New Zealand home of the

genus is indicated by a species in the intermediate Kermadec group. The

genus Astelia has been discussed on page 291. It is represented in

Hawaii and in most of the oceanic groups of elevated islands. The

solitary species, A. montana, discovered by Seemann on the summit of

Kandavu in Fiji, has since been found in Samoa, and probably Mr. Horne’s

collections contain another species.

The Rubiaceous genus Coprosma needs a few special remarks, since a

particular genus of birds seems to have been concerned in dispersing it

in the South Pacific. About fifty species are enumerated in the _Index

Kewensis_, and if we include a few other species from the collections of

Hillebrand, Horne, Cheeseman, &c., the total would be about sixty. Of

these, about half are restricted to New Zealand, which may be justly

regarded as the home of the genus, the rest being confined to Australia

and the islands of the Pacific, excepting a Chilian and three or four

Malayan species. Hawaii with its nine species, Tahiti with two,

Rarotonga with one, and Fiji with two or three species represent

approximately the distribution of the genus in the oceanic archipelagoes

of the tropical Pacific. (It most probably exists on the high peaks of

Samoa, though it has not yet been recorded from the group.) In all, or

in almost all cases, the species are restricted to their particular

groups, so that we may regard the dispersal of the genus over the

Pacific as suspended, though, as will be observed below, the period of

suspension in the South Pacific has not been of sufficient duration to

obliterate the affinities of species in distant groups and to prevent us

from tracing out the route followed by the genus.

This genus of temperate latitudes, which in its New Zealand home ranges

from near the sea-level to the region of the alpine floras, finds its

usual station in the tropics on the summits of mountains. Thus, on Mount

Kinabalu, in Borneo, it is found at altitudes of 10,500 to 13,000 feet

(Stapf), and on the mountains of East Java at elevations exceeding 9,000

feet (Schimper). In Hawaii its species grow at elevations ranging from

3,000 to 9,000 feet, and in Tahiti at altitudes of 2,600 to 3,300 feet;

whilst in Rarotonga it grows in the hilly parts of the island, its

elevation in Fiji not being recorded.

When we come to consider the route by which the genus (Coprosma) entered

the tropical Pacific, we must remember that unless we establish some

special connection with its New Zealand home it will always be open for

any one to suggest that the genus might have been derived, like

Vaccinium, from other regions than the south, as from the summits of the

Malayan mountains. However, a curious connection has been discovered by

Mr. Cheeseman in his examination of the Kermadec and Rarotongan floras,

and it would indeed appear that he has traced the Rarotongan peculiar

species to its New Zealand home. Thus, he says that Coprosma lævigata,

his new Rarotongan species, is very closely allied to the Kermadec

endemic plant, C. acutifolia, Hook., which itself comes near C. lucida,

Forst., a New Zealand species. The connection between Rarotonga and New

Zealand by way of the Kermadec group is rendered yet more probable by

the occurrence of two New Zealand species of Coprosma in the Kermadec

flora (_Journ. Linn. Soc._ i. 1857; _Trans. Linn. Soc. Bot._ vi. 1903;

_Trans. N.Z. Instit._ xx. 1887).

When speaking of the genus in Hawaii (page 275), mention was made of the

inter-island dispersal of the fruits of one of the species by the native

mountain-goose, Bernicla sandwicensis. We learn from Sir W. Buller’s

_History of the Birds of New Zealand_ that when the Coprosma is in fruit

the Swamp-Hens (Porphyrio melanotus) come out to feed on it. These

birds, he says, are capable of prolonged flight; and I chance to have

beside me a cutting from the _Field_ of July 9, 1904, in which “Hy. S.”

refers to a Black-backed Porphyrio that was captured in 1876 four

hundred miles off the coast of New Zealand. This genus, which is widely

dispersed in the tropics, the birds being commonly known as Sultanas,

Blue Gallinules, Purple Water-Hens, &c., has probably been a very

important factor in the dispersal of plants, especially in connection

with insular floras. The birds live on a variety of food. The Messrs.

Layard observed that Porphyrio vitiensis, which abounds in the swamps of

New Caledonia, fed on maize, yams, &c. (_Ibis_, 1882); whilst in the

stomach of a bird of the same genus shot in the Rewa swamps in Fiji I

found a number of the stony fruits of Scleria, a genus of the Cyperaceæ.

According to Mr. Wiglesworth, each region in the South Pacific has its

own species of Porphyrio. There is one in the Tahitian Islands, and

another common to Fiji, Tonga, and Samoa; whilst New Caledonia and the

New Hebrides have their species (“Aves Polynesiæ”). However, it is

evident that the power of dispersing seeds from group to group is not

quite suspended, since, as we learn from Sir W. Buller, the New Zealand

species, above named as partial to Coprosma drupes, is distributed over

Tasmania and Australia, and reaches also Niue and New Caledonia; whilst

the Messrs. Layard evidently regarded one species as common to Fiji and

New Caledonia.

It is doubtless to birds of this description that we owe some of the

specific connections of Coprosma between groups of the Western Pacific.

That the dispersal of the species over distant regions was recently in

active operation is shown by the close affinity, according to Dr. Stapf,

of two species growing on the summit of Kinabalu, the Bornean mountain,

with certain species from New Zealand and South-east Australia. Other

Rubiaceous species, like Nertera depressa, possessing Coprosma-like

fruits and fitted for the same mode of dispersal, link the heights of

Kinabalu with the flora of high southern latitudes.

Being included in the Fijian area, the scanty mountain-flora of Samoa

may be here referred to. As in Fiji, the endemic genera of Compositæ and

Lobeliaceæ are not to be found, but we find in the central elevated

district of Savaii, which rises to over 5,000 feet above the sea, a

peculiar species of Vaccinium (4,900 feet), the Antarctic Nertera

depressa (4,000 feet), and two species of Weinmannia, a genus hailing

probably from high southern latitudes.

THE FIJIAN CONIFERÆ.

It has been found most convenient to discuss here these interesting

plants, which belong in a general sense to the mountain-flora of this

archipelago. That which the Fijian flora loses in interest in the eyes

of the student of plant-dispersal in not possessing the mysterious

Composite and Lobeliaceous genera of Hawaii and Tahiti, it regains in

the possession of its genera of Coniferæ. If he felt loth to apply his

empirical principles to the above-named Hawaiian and Tahitian endemic

genera, he feels more than uneasy when he comes to deal with the three

Coniferous genera of Fiji, Dammara (Agathis), Podocarpus, and Dacrydium.

These three genera represent an order that has not found a home either

in Tahiti or in East Polynesia generally, or in the more distant Hawaii;

and they present at first sight in their existence in Fiji a powerful

argument in favour of the previous continental condition of the islands

of the Western Pacific. But in advocating this view we should remember

that it involves the original continuity of the Fijian land-area, not

only with the neighbouring islands of the New Hebrides and of New

Caledonia where these genera alike occur, but also with New Zealand,

Tasmania, and Australia, where they sometimes attain a great

development.

In Fiji these trees often chiefly form the forests of the larger

islands, extending in the moister regions from near the sea to the

mountain-tops, and being often abundant on the great mountain-ridges of

the interior. It may be at once remarked that, viewed merely from the

standpoint of dispersal, there is no great difficulty in regarding it as

probable that the seeds of Podocarpus and Dacrydium have been dispersed

by frugivorous birds over tracts of ocean 500 or 600 miles across.

Dammara, however, so far as my Fijian observations show, possesses none

of the means of dispersal across oceans that we are at present

acquainted with. The two first-named genera occur in South America as

well as in the Australo-Polynesian region, some of the species in these

two regions, though the Pacific Ocean divides them, being closely

related. Dammara is, on the other hand, confined to a much more limited

area, extending from New Zealand to Borneo. It is from the distribution

of this genus that the continental theory derives its chief support.

Yet it may be remarked that something more than questions relating to

the capacity for dispersal are involved here. This is at once indicated

by the circumstance that although Podocarpus is known to be dispersed by

frugivorous birds, it is not found in Polynesia east of Tonga, and the

same may be said of Dacrydium, which does not occur east of Fiji. In

this connection it is necessary to notice the intrusion of Araucaria

into the tropical Pacific from Eastern Australia to New Caledonia and

the New Hebrides. The fact of this genus not having been recorded from

Fiji or any of the groups east of the New Hebrides is very remarkable,

and scarcely in accordance with the continental hypothesis. There is a

persistence in type of these genera of the Coniferæ during geological

time that prevents us from dealing with them on the lines that are

required by the mass of the flowering-plants. Other factors intervene,

and we apply with hesitation the same canons of dispersal that we employ

for the general bulk of the plants of the Pacific islands. If, as often

happens, a specific distinction alone separates the Conifers of the same

genus on either side of the Pacific Ocean, it must possess in point of

time a very different value from that which we would usually attach to

specific distinctions in the floras of the Pacific islands.

DAMMARA (AGATHIS).—The Dammara region includes Eastern Australia, New

Zealand, New Caledonia, with the New Hebrides, Fijian, and Santa Cruz

groups, and extends north-west to Java and Borneo. Only ten species are

named in the _Index Kewensis_, and of these four are assigned to New

Caledonia and two to Fiji, the focus of geographical distribution being,

therefore, as Seemann long since pointed out, in the islands of the

Western Pacific. The absence of the genus from the neighbouring Samoan

and Tongan groups is very significant; and it is evident that the

ordinary agencies of dispersal, whether birds, winds, or currents, have

here failed to extend the genus over a few hundred miles of sea.

When by means of observation and experiment we turn to the fruits and

look for a reply, we find in the first place that they are never to be

noticed either whole or in part in the floating drift of sea or river,

or amongst the stranded materials of the beaches. This is at once

explained when we ascertain that the fresh cones sink in the

river-water, and thus could never reach the coast in their entire

condition. Nor could they do so in fragments, since the detached cone

falls to pieces on the ground and the separate scales and seeds sink at

once or float only for a few hours. In order to test the buoyancy of a

cone after drying, it is necessary to bind it round with string to keep

it from breaking down. One such fruit, after being kept for ten days,

was placed in sea-water, where it floated heavily for eleven days and

then sank. This is, of course, a most unnatural experiment, but it was

well to have carried it out. That the entire fruit could never be

transported by water is indirectly implied by Kirk respecting the fruit

of Dammara australis, the Kauri Pine of New Zealand. In this case, when

the fruit reaches maturity the scales, he remarks, fall away from the

woody axis of the cone and the seeds are freed.

The fleshy, unprotected seeds, which, as above noted, possess little or

no floating power, could scarcely withstand the injurious effect of

sea-water; and they are absolutely unfitted for any known mode of

dispersal by birds. It is observed by Kirk that the seeds of the New

Zealand tree are widely spread by winds. But this could only avail them

for local dispersion, and they appear ill-suited for being transported

for more than a few paces. The seeds are winged, and are in form a

little like the samara of the Maple (Acer); but they have not the same

protective coverings, the wing being, however, only a little more than

half the length of the entire seed. Those of both Dammara australis and

D. vitiensis are about two-thirds of an inch in length, and are

heavy-looking; and the agency of the wind could never be invoked except

for local dispersion.

Looking at these results, the cones of Dammara may be regarded as most

unsuited for any of the ordinary means of dispersal over an ocean except

through the agency of man. There is, however, no necessity to introduce

man’s aid here, unless the gum or resin which the Fijian burns in his

torches and employs as a glaze for his pottery gave his ancestors an

object in carrying the cones with them in their migrations. But in that

case the same argument would have to be applied to all partially useful

plants, and much of the Fijian flora would lose its indigenous

reputation. The endemic character of the Fijian species also militates

against such a view, and we should have to apply the same explanation to

the New Zealand species, concerning which no one, so far as I know, has

ever ventured to suggest that it was introduced by the Maoris.

The native names of the trees seem to have been sometimes connected with

general words for gums or resins; whilst at other times the tree and the

resin have separate designations. Thus the Fijians call the tree

“ndakua” and the resin “makandre,” which last Hazlewood in his

dictionary seemingly connects with “ndrenga,” the word for “gum.” In my

work on the Solomon Islands, page 190, I have endeavoured to show that

the Maori name of “kauri” may be connected with “gatah,” the general

Malayan word for gums and resins, transitional stages being presented in

the names of resin-yielding trees in the intermediate regions, as, for

instance, by “gutur,” a species of Canarium, on the Maclay coast of New

Guinea, and by “katari,” a species of Calophyllum, in Bougainville

Straits, Solomon group. It may be pointed out that these facts of

plant-nomenclature do not promise us any aid in determining the mode of

dispersion of Dammara in the Western Pacific. There is a suspicious

resemblance between the Fijian name of “ndakua” and “dundathu,” the

Queensland aboriginal name for Dammara robusta; but even if the

comparison is legitimate, its explanation may lie far back in the ages

in some root-word as ancient as the Malayan “gatah.”

If there is a real difficulty in applying our canons of

plant-dispersal to the distribution of Dammara, it is merely the same

difficulty that has so often perplexed the botanist with other

Coniferous genera in continental regions, such as, for instance, the

occurrence of Pinus excelsa on the far-removed mountains of Europe and

of the Himalayas, and the existence of the cedar in its isolated homes

on the Atlas, the Lebanon mountains, and the Himalayas. Such

difficulties largely disappear if we regard the present distribution

of the Coniferæ as the remnant of what it was in an ancient geological

period. In the case of Dammara it seems almost as idle to puzzle over

its means of dispersal as to consider the mode of dispersal of the

Marsupials. The questions, indeed, that affect the Dammaras of Fiji

and the Western Pacific far ante-date any questions concerning a

previous continental condition of those regions. The attitude of the

palæobotanist to such questions would probably be one of indifference;

yet to the student of plant-distribution they are of prime importance;

and _nolens volens_ we must admit that Dammara may well be cited in

support of any continental hypothesis affecting the Western Pacific.

PODOCARPUS.—In this connection I will mainly depend on Pilger’s recent

monograph on the Taxaceæ (heft 18, Engler’s _Das Pflanzenreich_, 1903).

More than sixty species are here enumerated, which are distributed in

Africa, Asia, Australasia, and South America. With a range that extends

north to Japan and south to Southern Chile in latitude 48°, this genus

attains its greatest development in respect of species in Malaya, in the

region comprised by Australia, New Zealand, and New Caledonia, in South

America, and in Africa. Eastward of New Caledonia it is found in Fiji

and in Tonga, but not in Samoa, and it is altogether absent from the

Tahitian region as well as from Hawaii. Of the four species accredited

by Seemann to Fiji, two are enumerated by Pilger, namely, P. affinis and

P. vitiensis. The first-named, according to Stapf, is allied to P.

bracteata, which occurs on the upper slopes of Kinabalu, in Borneo, and

is distributed not only over Malaya, but occurs in Japan and in the

Himalayas. The Tongan species, P. elatus, is, according to Hemsley,

found in East Australia.

This Tongan tree is suggestive of bird-agency in the dispersal of the

genus, and the same may be said of the occurrence of another species, P.

ferrugineus, found in both New Caledonia and New Zealand. Since the

seeds of the genus possess an outer fleshy and an inner bony covering,

they would appear to be well fitted both to attract and to be dispersed

by birds. In fact, we learn from Sir W. Buller that the New Zealand

fruit-pigeon feeds on the seeds of the “matai” tree (Podocarpus spicata)

and of the “kahikatea” (P. dacrydioides), and no doubt to the agency of

frugivorous birds we can attribute the presence of the genus in Fiji and

Tonga. Yet it is strange that bird-agency should have failed both with

Tahiti and Hawaii. In point of size the seeds, which range from

one-quarter to an inch across, present no great difficulty, and one

would have thought that the birds that carried the “stones” of

Elæocarpus to Hawaii could have also carried the seeds of Podocarpus.

It is, however, necessary to remember, in dealing with a genus that has

a wide distribution both in time and space, that specific affinities may

have a very different significance with the Gymnosperms than with most

other flowering plants. When Hemsley remarks (_Introd. Chall. Bot._ p.

56) that the New Zealand Podocarpus spicata is closely allied to the

South American P. andina, he does not imply that the two regions are in

touch with each other though some 5,000 to 6,000 miles of ocean

intervene. One is prepared to credit these seeds with a capacity of

dispersal by birds over tracts of sea such as the extent of ocean

separating New Caledonia and New Zealand, which are some 900 miles

apart; but one hesitates to admit that frugivorous birds could carry

them across the Southern Ocean. If we assign a home in the high

latitudes of the northern hemisphere to a genus that was well

represented in Europe in the Tertiary period, a movement of migration

southward would explain most of the difficulties in its present

distribution. The great vertical range of some of the species leads us

to attribute a corresponding power of adaptation to the genus in respect

of widely different climates. Thus, according to Stapf, the vertical

range of P. bracteata in the Malay Archipelago extends, including

varieties, from the coast to an altitude of 12,000 feet. With such a

capacity for adaptation, migrations of the genus would be rendered easy

over the globe.

DACRYDIUM.—It may happen that some additional light on the mystery of

the Fijian Coniferæ may be afforded by Dacrydium elatum, a tree that

occurs not only in Fiji, but in Further India and in Malaya. Pilger

confirms Seemann’s view in his identification of the Fijian tree, and

this opinion is, in the main, shared by Stapf. This species, so to

speak, affords us a _point d’appui_ in the history of the distribution

of the genus in the Western Pacific. This distribution somewhat

resembles that of Dammara in extending from New Zealand (its principal

centre) to Malaya and Further India; but, unlike Dammara, Dacrydium is

represented in America by a solitary species in South Chile. Of the

sixteen species enumerated by Pilger, seven belong to New Zealand, four

to New Caledonia, three to Malaya, one to Tasmania, and one to Chile.

The seeds are, as a rule, smaller than those of Podocarpus, and on

account of their somewhat similar structure would serve as bird-food,

and might be distributed in this fashion. Yet the genus has been only

recorded from Fiji, and is not only unrepresented in Hawaii and Tahiti,

but is also not known from the Tongan and Samoan groups that belong to

the Fijian floral region of the Pacific. Capacities for dispersal appear

meaningless here, especially when we have regard to the solitary

American species, Dacrydium fonkii, that as a shrub finds a refuge in

the bleak region of Southern Chile.

The three Fijian genera of the Coniferæ, Dammara, Podocarpus, and

Dacrydium, appear at first sight to be beyond the reach of our canons of

plant-dispersal, by which we connect specific affinity with a continuity

of range, and by which we co-ordinate means of dispersal and area of

distribution. We begin to realise that there may have been an age of

Coniferæ in the Pacific islands that is even less amenable to our

methods than the later era of the Compositæ and Lobeliaceæ in Hawaii and

Tahiti. Such an age would be concerned only with that region in the

Western Pacific which is now held by the genera Dammara, Podocarpus, and

Dacrydium, a region that did not participate in the era of the Compositæ

and Lobeliaceæ. We thus have evidence of an ancient era of the Coniferæ

that was confined to the Western Pacific, and of a later era indicated

by the peculiar genera of Compositæ and Lobeliaceæ that was restricted

to Hawaii and to Eastern Polynesia (Tahiti, Rarotonga, &c.). The key to

the situation here presented seems to lie in the following

considerations.

It is assumed that there was an age of Coniferæ in the Pacific, or

rather that this region shared in an era of dispersion of existing

genera of the order. In this age only the islands of the Western Pacific

participated, neither the Hawaiian nor the Tahitian islands taking a

part in it. Such a result is to be attributed either to the inability of

these genera of Conifers to reach Hawaii and the islands of East

Polynesia, or to the non-existence of the Hawaiian and Tahitian

archipelagoes at that epoch. The first explanation seems scarcely

acceptable, since, although the powers of dispersal of the genus Dammara

are very limited, there seems no reason why the genera Podocarpus and

Dacrydium could not have reached those distant regions of the Pacific.

The second explanation is most probable, and it is the one suggested by

Hillebrand (p. xxx) in the case of Hawaii, namely, that “the absence of

Gymnosperms militates for the view that the islands were formed

subsequent to the age in which these were universally distributed.”

If this conclusion is legitimate we have here a datum-mark in the

history of the islands of this ocean. Before the appearance of the

Hawaiian and Tahitian islands (using the term Tahitian to cover the East

Polynesian region) there existed a land-area in the Western Pacific held

by the Coniferæ, probably in the late Secondary period. After the

formation of the Hawaiian and Tahitian islands, perhaps in the early

Tertiary epoch, came the age characterised by the ancestors of the

present endemic genera of the Compositæ and Lobeliaceæ, and of a few

other orders in Hawaii and Tahiti. In this age the islands of the

Western Pacific do not seem to have participated, and it is to be

inferred that this was an age of extensive but probably not of complete

submergence in that part of the ocean, since at least the genus Dammara

was able in places to hold its ground. Then ensued the great Tertiary

emergence of the land-areas of the Western Pacific, when small islands

that dotted the sea-surface in this region became the nuclei for the

formation of the large islands of the present Fijian, New Hebrides, and

Solomon groups. This prepared the way for the migration of Malayan

plants which now predominate over the islands of the tropical Pacific;

and in a later age man, following the same track from Indo-Malaya,

occupied these islands.

In my volume on the geology of Vanua Levu it was shown that the Tertiary

period was an age of submergence in the Western Pacific, and a disbelief

in any previous continental condition was expressed. My later view is

more in accordance with that of Wichmann, who, on geological grounds,

contended that the islands of the Western Pacific were in a continental

condition during the Palæozoic and Mesozoic periods, and that their

submergence and subsequent emergence took place in Tertiary times. The

distribution of the genus Dammara has thus led me to modify the views

expressed in the final chapter of my first volume on the geology of

Vanua Levu. Though still holding that there is no geological evidence

that the various islands of the Fijian group were ever amalgamated, or

that they were joined as such to the westward groups, it is quite

possible that their position was indicated by a few small islands a few

miles across and a few hundred feet in height in early Tertiary times.

On these small islands, which probably represented the remains of a

submerged Mesozoic land-area, such as is in part implied in Dr. Forbes’

_Antipodea_, or in Mr. Hedley’s _Melanesian Plateau_, the genus Dammara

survived. Such islands merely indicated the situation of some of the

present groups of the Western Pacific, which have been since largely

built up by submarine eruptions, and the greater number of the islands

were no doubt completely submerged. Between the groups as we know them

now there never was any land connection, since they are the product of

later eruptions, mainly submarine; and they have acquired their present

composite character during the emergence that followed the period of

volcanic activity. Except, perhaps, in New Caledonia, which does not

seem to have shared in the Tertiary submergence, the islands of the

Western Pacific have a configuration acquired in comparatively recent

times, and one that gives no idea of the character of the Mesozoic

continent.

Such, as I understand them, are the indications of the Fijian Coniferæ

and particularly of Dammara. In the distribution of this genus we have

outlined an ancient, more or less continuous land area which, with the

exception of a few isolated points, disappeared beneath the sea in

Tertiary times to re-appear near the close of that period in the form of

a number of archipelagoes that were largely built up by submarine

eruptions, and probably altogether mask the form of the original

land-area. It may be remarked that New Zealand, which largely shared in

the Tertiary submergence, especially in the Miocene age, is included in

the range of the genus Dammara, as well as in those of the genera

Podocarpus and Dacrydium.

_Summary._

(1) The evidences of a mountain-flora in Tahiti, as indicated by the

non-endemic genera, though, as we would expect, of a scanty nature when

contrasted with Hawaii, are nevertheless of considerable interest. There

is much kinship with the Hawaiian mountain-flora, but it is mainly

confined to genera from high southern latitudes, such as Nertera,

Coprosma, Cyathodes, and Astelia, which are all dispersed by frugivorous

birds. Amongst other plants linking the Tahitian mountains with the

region of the Antarctic flora, and with New Zealand in particular, may

be mentioned Coriaria ruscifolia and the genus Weinmannia.

(2) On account of their relatively low altitude the Fijian islands do

not present the conditions for an alpine flora. Traces, however, of the

Antarctic flora, or of the New Zealand flora, occur on occasional

mountain-tops, as is indicated by the occurrence of species of

Lagenophora, Coprosma, and Astelia. In Samoa the mountain-flora is also

scantily developed, as we might have expected; but here occurs the genus

Vaccinium as well as a widely-ranging species of the Antarctic flora,

Nertera depressa.

(3) The route by which some of the representatives of the flora of high

southern latitudes reached the mountains of the islands of the tropical

Pacific is directly indicated by the genus Coprosma to have been from

New Zealand by way of the Kermadec Islands.

(4) In the distribution of plants possessing drupes or berries that

connect the tropical islands of the South Pacific with New Zealand, it

is highly probable that birds of the genus Porphyrio (Swamp-Hens or

Purple Water-Hens) have taken a prominent part.

(5) In the possession of species of the three genera of Coniferæ,

Dammara, Podocarpus, and Dacrydium, which often largely form the forests

of the mountain-slopes, Fiji is distinguished from all the other groups

of the open Pacific with the exception of Tonga, which owns a species of

Podocarpus probably introduced by birds. From the circumstance that

Dammara has no known means of crossing a tract of ocean, whilst

Podocarpus and Dacrydium could be dispersed by frugivorous birds, all

three genera having, however, much the same limited distribution in the

Western Pacific, it is apparent that something more than a question of

means of dispersal is here involved. It is assumed that they mark the

site of a Mesozoic continental area in this region, and that at this

period the Tahitian and Hawaiian groups which possess no Conifers did

not exist. This area was submerged during the Tertiary period with the

exception of a few peaks that formed small islands on which the Conifers

held their ground. During the Tertiary submergence of the Western

Pacific region, the Hawaiian and Tahitian islands were built up by

subaërial volcanoes and received the ancestors of the Compositæ and

Lobeliaceæ that now exist as endemic genera in those groups. Then

followed the emergence of the islands of the Western Pacific and their

occupation mainly by Indo-Malayan plants that extended eastward over the

Pacific. Thus in the Pacific there has been first an age of Conifers in

which the islands of the Hawaiian and Tahitian regions could not

participate, since they did not exist. Then ensued an era of American

forms of Compositæ and Lobeliaceæ in which only Hawaii and Tahiti

participated, since the Western Pacific region was submerged. Lastly

came the invasion of Indo-Malayan plants, which have largely occupied

every group in the tropical Pacific.

CHAPTER XXV

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

THE AGE OF THE MALAYAN PLANTS AS REPRESENTED IN THE LOW-LEVEL FLORA OF

HAWAII AND IN THE BULK OF THE FLORAS OF THE FIJIAN AND TAHITIAN REGIONS

_The Age of Wide Dispersal over the Tropical Pacific._

The widely dispersed genera which possess only peculiar species in

Hawaii.—Pittosporum.—Reynoldsia.—Gardenia.—Psychotria.—Cyrtandra—Freycinetia.—Sapindus.—Phyllanthus.—Pritchardia.—Summary.

WE pass now from the consideration of the mountain-flora of Hawaii and

its scanty representation in the Fijian and Tahitian regions to a

discussion of the low-level Hawaiian flora, belonging to stations under

4,000 or 5,000 feet, and of the corresponding floras of the other two

regions. It has been previously pointed out that in mass the plants of

Fiji and Tahiti correspond to the low-level flora of Hawaii.

There are numerous ways of comparing this era of the non-endemic genera

of these three regions of the Pacific. The necessities of space,

however, compel me to treat the subject only in an illustrative fashion,

and in adopting the plan which seems easiest and simplest I have also

been obliged to keep my limitations mainly in view.

THE WIDELY-DISPERSED GENERA WHICH POSSESS ONLY PECULIAR SPECIES IN

HAWAII.

Amongst the oldest denizens of the Pacific islands in this era of the

non-endemic genera may be taken those genera of flowering plants which

are found in all three regions, Hawaii, Fiji, and Tahiti, but possess in

the first group only endemic species, whilst in the other two regions

they may include species both confined to and occurring outside the

respective groups. They represent an age of wide dispersal over the

Pacific, an age which for Hawaii has long since passed away, since all

the genera have been disconnected from the outer world, whilst in the

groups of the South Pacific they as a rule in each case remain in touch

through some of the species with the groups around.

Observations of a Naturalist in the Pacific Between 1896 and 1899, Volume 2 Plant-Dispersal · 第 39 / 47 章

With regard to the absence of these arborescent Lobeliaceæ from the