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. — 

 . Acaena, 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 Compositae and 

 Lobeliaceae, 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 com- 

 posed entirely of species not found outside the group ; and in 



