144 A NATURALIST IN THE PACIFIC chap. 



Erythrina monosperma, it may be remarked that this is precisely 

 what has happened with the seeds of Caesalpinia bonducella, its 

 usual associate on the old lava-wastes in Hawaii, and with an 

 inland species of Caesalpinia in Fiji. It is argued that the same 

 thing has occurred with the inland Hawaiian species of Canavalia 

 and Sophora, as shown in later pages of this chapter. It has 

 certainly happened with the inland form of Afzelia bijuga in Fiji^ 

 a tree dealt with in Chapter XVII. These are all Leguminous 

 genera ; and in all of them, with the exception of Caesalpinia, 

 where the floating power arises from a central cavity in the seed^ 

 the seeds of the littoral species possess, like Erythrina indica, 

 buoyant kernels. Whilst most littoral plants with buoyant seeds 

 or fruits retain the floating capacity of the seed or fruit when 

 they extend inland, the Leguminosae often offer exceptions to the 

 rule. 



That inland endemic species of Erythrina can be developed 

 in isolated islands is illustrated by the existence in Fernando 

 Noronha, some two hundred miles from the coast of Brazil, of a 

 peculiar species, E. aurantiaca, described by Mr. Ridley. Here 

 also is found an inland species of Guettarda peculiar to the locality; 

 but in neither genus does the littoral species occur. 



Many difficulties will yet have to be explained before it can be 

 finally established that Erythrina monosperma has been derived 

 from E. indica or some similar shore species that was originally 

 dispersed by the currents ; but we are almost driven towards such 

 a view, since it is hard to believe that the beans were carried to 

 Hawaii by birds over some two thousand miles of sea. Observers 

 in other regions where littoral and inland species of the genus occur 

 may perhaps devote their attention to the relation between the 

 two ; and if they are able to supplement observation and 

 experiment by a microscopical investigation, some interesting 

 results would be obtained. For instance, I would suggest that in 

 Queensland a thorough examination of the littoral E. indica and 

 the inland E. vespertilio might be undertaken ; or perhaps there 

 may be some other littoral form. 



With the two other Leguminous genera, Canavalia and 

 Sophora, to be immediately discussed, we have for the most part 

 the same questions raised. Both possess wide-ranging current- 

 dispersed littoral species in other parts of the Pacific, but only 

 endemic inland species with non-buoyant seeds in Hawaii. The 

 pivot of the discussion will be here also the impracticability of 

 these inland species ever having reached the Hawaiian Islands 



