XXVII STERCULIA 



391 



halted in the Fijian region because they entered the Pacific after 

 the age of active general dispersal over that ocean. 



Occasionally we notice in this region that which we have 

 observed in the case of Cyrtandra in different Pacific groups, 

 namely, a sudden development of what Hillebrand terms " formative 

 energy " in a genus, such as we find in the case of Elatostema in 

 Samoa, and in that of Psychotria in Fiji and Samoa. The principle 

 of polymorphism in the development of species is also illustrated 

 by Micromelum and by Limnanthemum. In the last case we 

 possess a typical polymorphous species in Limnanthemum indicum 

 that has played in this respect the role of Naias marina in the warm 

 waters of the globe. 



With several genera that like Gnetum, Myristica, and Sterculia 

 occur both in the Old and the New World, it is evident that in 

 explaining their distribution we are dealing with something more 

 than questions of means of dispersal. With these genera, and with 

 others like Lindenia, it seems almost futile to talk of means of 

 dispersal, when to all appearance their existing distribution is but 

 the remnant of an age of general dispersion over the greater part 

 of the warm regions of the world. These genera, with others, might 

 be cited in favour of the continental hypothesis relating to the 

 islands of the Western Pacific. Trees with stone-fruits, such as 

 Canarium, Couthovia, Dracontomelon, and Veitchia, where the 

 stones are an inch and more in length, might be also adduced by 

 some in evidence of this theory. But in these cases the lesson of 

 Elaeocarpus (Chapter XXVI) should always be remembered, since 

 the " stones " of drupes may vary greatly in size amongst the 

 different species of a genus, and species seemingly " impossible " 

 from the standpoint of dispersal in one group may be represented 

 in other groups by species where the size of the " stone " presents 

 no difficulty in attributing the dispersal of the genus to frugivorous 

 birds. 



Sterculia 



The problem connected with the presence of this genus in Fiji 

 is but a part of the still more difficult problem connected with the 

 dispersal of the genus over the tropics. The riddle presented by 

 the Fijian species seems, indeed, difficult enough ; but it merely 

 presents in miniature the great mystery surrounding the whole 

 genus. According to the Index Kewensis no other species have 

 been found in oceanic islands except those occurring in the 

 Western Pacific, as in Fiji, the New Hebrides, and New Caledonia, 

 and most of these seem to be confined to those islands. We have 



