XV LITTORAL AND INLAND PLANTS' RELATIONSHIP 147 



galeata and Mezoneuron kauaiensis, two of the greatest riddles 

 presented by the Leguminosas of Hawaii. 



The flat seeds of this species of Mezoneuron measure about an 

 inch (2'5 cm.), and seem most unsuitable for dispersal by birds 

 over a wide extent of ocean. Nor can we appeal to the currents, 

 since my experiments in Hawaii show that the seeds have no 

 buoyancy and that the pods only float for a week in sea-water. 

 Dr. Hillebrand records this shrub from Kauai, Oaau, and Maui ; I 

 found it also on the lower slopes of Hualalai in Hawaii and there- 

 fore the same question of inter-island dispersal here presents itself 

 that was connected with Canavalia galeata, since we have also to 

 explain the transport of the seeds between islands 70 to 1 50 miles 

 apart. The critical point in the history of these two enigmatic 

 inland plants of the Hawaiian Islands was doubtless concerned 

 with the loss of buoyancy of the seeds of the original littoral plant. 

 It will subsequently be shown that this is what is now in actual 

 operation with Caesalpinia and Afzelia in different parts of the 

 Pacific. 



SOPHORA. 



In this genus, as in Erythrina and Canavalia, we have a littoral 

 species, Sophora tomentosa, that ranges over the tropical beaches 

 of the globe, including most of the islands of the Pacific, but does 

 not occur in Hawaii, where the genus is represented by an endemic 

 inland species, S. chrysophylla. Here also we find the shore- 

 species with seeds capable of floating for months on account 

 of their buoyant kernels, and the inland species with seeds 

 that sink even after years of drying (see Note 56). Unless other 

 inland species of Sophora have recently been described from the 

 tropical Pacific, the Hawaiian species is the only one of its kind 

 known from this region. 



But the problem wears a different aspect in the case of this 

 genus, since the endemic inland species of Hawaii is a tree of the 

 mountains where a temperate climate prevails, whilst Sophora 

 tomentosa is a shrub of the tropical beach that only at times 

 extends into subtropical latitudes. The Mamani tree, as the 

 Hawaiians name S. chrysophylla, extends up to 9,000 or 10,000 

 feet above the sea, forming, with Myoporum sandwicense and one 

 or two other trees and shrubs, the hisjhest belt of the forest in the 

 larger islands. It is in the open woodland between 6,000 and 

 7,000 feet that it is most at home, and here it attains a height of 

 20 to 30 feet. It descends in places to as low as 2,000 feet above 



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