XXI THE AGE OF COMPOSITvE 247 



field of inquiry, quite beyond the scope of ttiis work. There is, 

 however, an inference that I think we may legitimately draw from 

 geological evidence in this region. With respect to the antiquity 

 of the woody Compositse of the Pacific as illustrated by the 

 endemic genera, both Mr. Bentham and Mr. Hemsley view them 

 as belonging to ancient types. Mr. Wallace, in his Island Life, a 

 book that becomes more and more indispensable for the student of 

 dispersal as years progress, dwells on the importance of these 

 ancient Compositse in the floral history of the Pacific islands. W^e 

 may look upon the Hawaiian Compositae, he remarks, as represent- 

 ing the most ancient portion of the existing flora, carrying us back 

 to a very remote period when the facilities for communication with 

 America were greater than they are now. The date of this period 

 of oceanic dispersal of the Compositae we can now approximately 

 determine, since these plants are absent from the Fijian region, an 

 area of submergence during the Tertiary era. Before the island- 

 groups of the Fijian region had emerged towards the close of the 

 Tertiary period the achenes of the early Compositae had been 

 dispersed far and wide over the tropical Pacific. 



But this is not all that we can infer from the convergence 

 of these independent lines of botanical and geological investiga- 

 tion. Mr. Bentham observes that the tribes of the Compositae had 

 acquired the essential characters now employed in classification 

 before the dispersion of the order over the Pacific. Since this 

 general dispersion took place, as we hold, during the Tertiary sub- 

 mergence of the island-groups of West Polynesia (Fiji, Tonga, 

 Samoa), it follows that the birth of the tribes of the Compositse 

 antedates that period. If this interesting order could supply 

 us with a " datum-mark " in the history of the Pacific floras, it 

 would be stated in terms of the development of specific and generic 

 characters, but not of those of a tribe. 



Summary of Chapter. 



(i) The Hawaiian Islands present the same contrast with the 

 Fijian and Tahitian groups as regards the development of new 

 species in the case of the flowering plants that they offer in 

 the case of the vascular cryptogams (ferns and lycopods). But 

 the contrast is intensified, and it is further emphasised as respecting 

 the flowering plants by the evolution of a large number of endemic 

 genera. 



