All plants introduced by the aborigines and the white man are excluded. In so doing, I have mainly followed Seemann, a safe guide in all matters relating to weeds and to cultivated plants. The flora of a Pacific island thus treated undergoes serious diminution in its extent. In the case of the Rarotonga flora, for example, which according to Cheeseman includes about 260 flowering plants, the number of truly indigenous plants, in the sense here implied, is only 140. Though this is an extreme case, it will serve to illustrate the principle here followed.
Table B (Flowering Plants).
Comparison of the Hawaiian, Fijian, and Tahitian genera. (All genera containing
introduced plants entirely are excluded.)
| Group. | Non-endemic genera. | Endemic genera. | Total. | ||||
|---|---|---|---|---|---|---|---|
| No endemic species. | Some species endemic, some not. | All species endemic. | |||||
| Hawaii | 70(31) | 30(13) | 95(43) | 28(13) | 223(100) | ||
| Fiji | S. 150(47) | S. 74(23) | S. 87(27) | S. 10(3) | S. 321(100) | ||
| H. 162(47) | H. 80(23) | H. 94(27) | H. 10(3) | H. 346(100) | |||
| Tahiti (Eastern Polynesia) | 125(66) | 21(11) | 40(21) | 4(2) | 190(100) | ||
Remarks.—The figures in brackets are percentages. S. = Seemann, H. = Horne and Seemann.
In the construction of this table, Hillebrand, Seemann, and Drake del Castillo have been mainly followed, except with regard to the endemic genera for Hawaii and Fiji. In this respect the Index Kewensis has been largely consulted as well as Engler’s publications, as indicated in the text. Hillebrand’s total of nearly forty Hawaiian peculiar genera and Seemann’s total of sixteen for Fiji have thus been considerably reduced. The two results given for Fiji are those of Seemann alone and with Horne superadded. Horne discovered, according to Hemsley, no new genera, but several genera from outside regions were added to the Fijian flora. Taking them as twenty-five (two-thirds of his own computation), I have apportioned them as in Seemann’s results. The Tahitian region here includes Eastern Polynesia.
It is necessary before proceeding further to obtain a correct idea of the significance of a large endemic element in the phanerogamic flora of a Pacific archipelago. We have therefore at the outset to inquire whether it is indicative of isolation or of antiquity. If the number of peculiar genera is to be regarded as the test of the relative antiquity of different Pacific floras and, by implication, of the islands to which they belong, these three groups, as shown in Table B, would arrange themselves in the following order, namely, Hawaii, Fiji, Tahiti. This test might be reliable if the several groups were in the same condition of isolation. Since, however, as we have previously seen, the Fijian Islands still enjoy a fairly free communication with the islands westward, whilst the Hawaiian group is largely cut off, it is apparent that the tendency to generic differentiation in Fiji might have been often swamped by immigration, and that Fiji with its much smaller number of endemic genera may even be older than Hawaii. This objection does not apply quite as forcibly to a comparison between Hawaii and Tahiti, yet for reasons before given it may be regarded as sufficient to negative any inferences concerned with relative antiquity.
On account, therefore, of the great differences in the degree of isolation of these three groups, we cannot be guided in our estimation of the relative antiquity of their floras by their number of peculiar genera. With the evidence at our disposal we are compelled to accept the view, which indeed a single glance at a map would suggest, that the number or proportion of endemic genera is to be connected with the degree of isolation. Whether a parallelism can be traced in the original stocking of these groups with their earliest flowering-plants is a matter that can only be elucidated by a further analysis of the peculiar genera.