222 



A NATURALIST IN THE PACIFIC 



CHAP. 



lycopods in the Tahitian and Hawaiian islands there are at least 

 half as many again in Fiji. When we reflect that the total areas 

 of the Fijian and Hawaiian groups are in each case about 7,000 

 square miles and that the extent of the whole Tahitian region does 

 not amount to 2,000 square miles, these facts acquire a fresh 

 significance. Ferns and lycopods might, therefore, be expected to 

 figure more largely in the Tahitian flora than in those of Fiji and 

 Hawaii ; and this is indeed the case. When we examine the 

 relative proportion of the vascular cryptogams to the indigenous 

 flowering plants in each area we find that whilst in Hawaii they 

 form about 18 per cent, of the total flora and in Fiji not much 

 more than this (see Note 62), in Tahiti they constitute just a third. 

 This excess of vascular cryptogams is reflected in the flora of the 

 outlying groups, the proportion in Rarotonga being, according to 

 Cheeseman, 30 per cent. It is, therefore, evident that in compari- 

 son with the other groups Tahiti possesses a marked preponder- 

 ance in ferns and lycopods. In this respect the Tahitian islands 

 resemble those of Juan Fernandez, where judging from the data 

 relating to the indigenous flora given in Hemsley's Botany of the 

 Challenger Expedition, the proportion of vascular cryptogams 

 amounts to between 30 and 38 per cent. 



But it has been already implied that the proportion of endemic 

 species of ferns and lycopods is from four to five times as large in 

 Hawaii as it is in Tahiti or Fiji. In Hawaii, therefore, there has been 

 a production of many new species, whilst in Fiji and Tahiti there 

 has been a great rush of immigrants. " Formative energy " in 

 Hawaii (to adopt an expression of Dr. Hillebrand) and " active 

 colonisation" in Fiji and Tahiti, such would appear to be the most 

 conspicuous features in the history of the vascular cryptogams of 

 these three archipelagoes. 



In these floras it is, therefore, apparent that respecting the vas- 

 cular cryptogams the average number of species in a genus does not 

 supply a means of contrasting them. As indicated in the table, 



Table of Vascular Cryptogams (Ferns and Lycopods) in the Groups of 

 Tahiti, Hawaii, and Fiji. (See note 63.) 



