3 i6 A NATURALIST IN THE PACIFIC CHAP. 



of the half-hundred species known from these groups, all but some 

 four or five are confined to particular groups. There is one species, 

 P. insularum, that ranges over the South Pacific from Fiji to the 

 Tahitian region ; and there are two or three others that keep up a 

 connection between the adjacent groups of Fiji, Samoa, and Tonga, 

 the last having no peculiar species ; but, apart from these indica- 

 tions, isolating influences generally prevail. The two Hawaiian 

 species are both endemic and are only recorded from the island of 

 Kauai, so that in that archipelago there has not even been inter- 

 island dispersal of the genus. For Fiji it would seem from the 

 Index Kewensis and other authorities that at least two-thirds of 

 the species are confined to the group. Of the dozen Samoan 

 species only two or three are known outside the islands. Four out 

 of the five Tahitian species are peculiar, and the only Marquesan 

 species named by Drake del Castello is endemic. Even the solitary 

 species of Juan Fernandez is endemic, there attaining the dimen- 

 sions of a fair-sized tree. It forms the subject of an illustration in 

 Schimper's Plant- Geography, page 491. 



Speaking generally, birds may be said to have almost ceased 

 dispersing this genus over the Pacific. This is not because birds 

 have ceased to be partial to the fruits, but because the frugivorous 

 birds that used to range over the Pacific archipelagoes now restrict 

 their wanderings to the limits of a single group. If we find 

 occasionally in other parts of the world, as in the occurrence of a 

 Florida species of Psychotria in the Bermudas, some evidence of a 

 dispersal still in operation, this is nothing more than we observe 

 in the case of a few of the Polynesian species now. The connection 

 between birds and plants in the Pacific is discussed in Chapter 

 XXX III. In this ocean the dispersal of the genus is now practically 

 dead, and Psychotria presents no exception to that general 

 tendency towards isolation and differentiation exhibited by most 

 genera of the tropical Pacific as the result of failure of the means 

 of dispersal. 



CYRTANDRA (Gesneracese). 



This remarkable genus of shrubs, which forms the subject of an 

 important memoir by Mr. C. B. Clarke (De Cand. Mon. Phan. v. 

 1883-87), offers, as Mr. Hemsley remarks, an example of a Malayan 

 genus extending to Polynesia and there developing numerous 

 species. Of some 180 known species, about 80 or nearly half are 

 confined to Polynesia, the rest being mainly Malayan. Of the 



