142 A NATURALIST IN THE PACIFIC chap. 



affects exposed dry rocky stations. In Hawaii, according to 

 Hillebrand, it is found on the dry rocky hills and plains of all the 

 islands up to i,ooo feet. I was particularly interested in this tree 

 whilst in the group, and found it in the large islands of Maui and 

 Hawaii thriving in rocky arid districts of little rainfall, accom- 

 panied by Cactus opuntia, Ricinus communis, and Caesalpinia 

 iDonducella. It is often to be observed on scantily vegetated lava- 

 flows, a solitary tree growing here and there out of a crack in the 

 old lava, or it may dot the rocky slopes of some barren declivity. 

 I found it in the dry gulches behind Lahaina at elevations of 800 

 to 1,200 feet above the sea, growing amongst huge blocks of 

 stone in clumps of ten or twelve trees. When one contrasts the 

 inland station of E. monosperma with that of E. indica on the beach 

 where the atmosphere is more humid and the conditions more 

 suited for plant-growth, it appears probable that the differences 

 between these two species may be largely connected with station, 

 especially as regards hairiness and the diminished size of the pods. 

 Assuming, therefore, that Erythrina monosperma is but the 

 inland form of E. indica and that the differences between the two 

 species are mainly an affair of station, we have next to account for 

 the occurrence of the inland species in Hawaii without the littoral 

 species. The agency of currents in explanation of the existence of 

 E. monosperma in Hawaii is at once excluded, since the pods 

 dehisce on the tree, and the seeds, as already remarked, have no 

 floating power. Nor does it seem likely that beans half an inch 

 (13 mm.) long could be transported unharmed in a bird's stomach 

 over the two thousand miles of sea that intervene between Tahiti 

 and Hawaii. Yet one cannot doubt that the pyrenes and 

 " stones " of genera like Coprosma, Nertera, Cyathodes, and 

 Osteomeles have been carried by frugivorous birds to Hawaii. 

 But a bean is somewhat different from the crustaceous pyrene of 

 Coprosma or the hard " stone " of Cyathodes ; and although, as 

 indicated by the occurrence of an endemic species of Erythrina in 

 Fernando Noronha, birds may carry large beans unharmed over a 

 couple of hundred miles of sea, one hesitates to conclude that they 

 could effect this when the tract of ocean to be traversed is ten 

 times as great. There are again reasons for believing that the 

 seeds of Erythrina monosperma are particularly ill-suited for 

 dispersal by birds, since, notwithstanding their hardness, they soon 

 absorb water through the micropylar opening ; and they germi- 

 nated so readily in my experiments that the digestive juices in a 

 bird's stomach would probably soon find access and destroy the 



