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.]