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I50 A NATURALIST IN THE PACIFIC chap. 



recalled that this is what happens to the seeds of Caesalpinia 

 bonducella and Afzelia bijuga when the plants extend inland 

 in the Pacific islands. It was held, in short, that the original 

 form of Sophora chrysophylla in Hawaii was a coast plant with 

 buoyant seeds, and therefore indebted for its presence to the 

 currents. Hailing from an extra-tropical region, it abandoned the 

 beach and found suitable conditions of existence in the moun- 

 tains, where it underwent specific differentiation. Such was the 

 explanation that presented itself to me on a Chilian beach. 



The first objection that offers itself against this view is that 

 Sophora chrysophylla is one of several species characterising the ^ 

 antarctic element of the mountain flora of Hawaii, and that many 

 of these plants, such as those of the genera Astelia, Coprosma, 

 Gunnera, Myoporum, &c., could only have reached these islands 

 through the agency of frugivorous birds (see Chapter XXIII.). 

 There is, therefore, something to be said for this mode of dispersal ; 

 but though one can understand how hard seeds and the " stones " 

 and crustaceous pyrenes of fleshy fruits might be transported 

 unharmed in a bird's stomach half-way across the Pacific Ocean 

 to the distant group of Hawaii, it is difficult to understand how 

 Leguminous seeds, except in such cases as Tephrosia piscatoria, 

 could be ejected unharmed by a bird after an ocean passage of some 

 1,500 or 2,000 miles. Yet evidence pointing to such a possibility 

 is not lacking. It was pointed out by W. O. Focke {Nat. schaft. 

 Ver. zur Bremen, Abhandl., Band 5, 1876) that for many Legu- 

 minosae we are driven to the agency of birds in order to explain 

 their dispersal. In this connection he mentions the case of a 

 pigeon killed by some beast of prey that he found in his garden in 

 the early winter. In the following spring he noticed numerous 

 .seedlings of Vicia faba sprouting up from amongst the feathers 

 that alone remained of the bird. In this observation he detected 

 the normal method of the dispersal of the Leguminosae by birds, 

 the seeds not being ejected by the bird but being set free by 

 its death. It is well known that Darwin had this idea in his mind 

 when he conducted his experiments on the dispersal of seeds ; and 

 reference may here be made to one that is recorded in More Letters 

 of Charles Darzvin (i., 436). Out of a number of seeds left in 

 the stomach of an eagle for eighteen hours, the majority were 

 killed ; but amongst the few that germinated afterwards was a seed 

 of clover (Trifolium). If such a bird had carried a Sophora seed to 

 Hawaii, this would have involved a continuous flight of, on the 

 average, 100 miles per hour for a period of fifteen to twenty hours. . 



