CHAPTER XV 



THE RELATION BETWEEN LITTORAL AND INLAND PLANTS 



{co?itinued) 



Inland species of a genus developed irom littoral species originally brought by 

 the currents but no longer existing in the group. — Illustrated by the 

 Leguminous genera, Erythrina, Canavalia, Mezoneuron, and Sophora, and 

 by the Apocynaceous genus, Ochrosia. — The Hawaiian difficulty. 



Section III 



Here we have three genera of the Leguminosae, namely, 

 Erythrina, Canavalia, and Sophora, and one Apocynaceous genus, 

 Ochrosia, in which it is considered that inland species have been 

 probably developed from littoral species no longer found in the 

 group. In this case the shore species, possessing buoyant seeds or 

 fruits that are known to be dispersed by the currents, is absent 

 from the particular group in which the inland species occurs ; and 

 since the last-named displays no capacity for distribution by 

 currents, or seemingly by birds, we are driven to infer that it was 

 originally derived from a coast species, brought by the currents, that 

 has since disappeared. 



Hawaii is the only region concerned here ; and these four 

 genera may be said to well illustrate the particular " Hawaiian 

 difficulty." If this explanation of the origin of the inland species 

 is legitimate, then it offers us a mode of explaining still more 

 perplexing cases in the Hawaiian flora, such as those relating to 

 the endemic species of Mezoneuron (Leguminosae) and to Hille- 

 brand's Vallesia (Apocynace^e), where there is apparently no 

 littoral species known from any region. 



Dealing with the three Leguminous genera, it is at first to be 

 remarked that the great floating powers of the seeds of the littoral 

 species are in all three cases to be attributed to the buoyant 



