20O A NATURALIST IN THE PACIFIC chap. 



is evident that Nature here takes advantage of a quality that could 

 never by its aid become a specific distinction. The upshot of the 

 selecting process wrould be the dispersal by the currents of nearly 

 empty seeds or seeds that have lost their germinating capacity. 



The distribution of the Leguminosae in the Pacific islands, and 

 indeed of tropical islands generally, is often full of inconsistencies. 

 This is the only order that sets at nought most of the principles 

 established for the other plants of the sea-coast, and that defies the 

 application of the laws of plant-dispersal now most in evidence. 

 Take, for instance, the inexplicable affinity of Acacia koa, the 

 well-known Koa tree of the Hawaiian forests, to Acacia hetero- 

 phylla, a tree restricted to the Mascarene islands of Mauritius and 

 Bourbon. Mr. Bentham, who placed them in the same group with 

 three or four Australian species, even doubted whether the differ- 

 ence between the Hawaiian and Mascarene species amounted to 

 specific rank. These two closely related Acacia trees of far-sepa- 

 rated islands of the Indian and Pacific Oceans represent outliers of 

 the great formation of phyllodineous Acacias that have their home 

 in Australia {Introd. Chall. Bot. p. 26). As far as I can gather 

 Acacia seeds have no known means of dispersal. Not even when 

 the tree has a littoral station, as in the case of Acacia laurifolia in 

 Fiji, have the seeds or pods any capacity worth speaking of for 

 dispersal by currents. We must appeal to the birds ; but to what 

 birds we may ask, unless it be to the extinct Columbae and their 

 kin, or to the Megapodes. Some of the other Hawaiian difficulties 

 connected with the inland Leguminosae are repeated in the Mascarene 

 Islands. Thus, Bourbon, like Hawaii, has its inland species of 

 Sophora of the section Edwardsia. 



In their irregular distribution the Leguminosae of the Pacific 

 islands are often a source of perplexity to the student of plant- 

 dispersal. Take, for example, the inland Erythrina, E. mono- 

 sperma, of Hawaii, Tahiti, and perhaps New Caledonia. Then 

 look at the singular distribution of the Sophoras of the Edwardsia 

 section in Chile and Peru, Hawaii, New Zealand, Further India, 

 and Bourbon. The botanist, again, finds a climber like Strongy- 

 lodon in the forests of Fiji, Tahiti, and Hawaii, and he picks up the 

 seeds on the beaches of those islands and notices that they float 

 unharmed for many months in the sea, yet when he pays heed to 

 the distribution of the genus he finds that it only comprises four or 

 five species, and that it occurs outside the Pacific only in the 

 Philippines, Ceylon, and Madagascar. The extraordinary distri- 

 bution of Entada scandens in the Pacific islands has been before 



