XV LITTORAL AND INLAND PLANTS' RELATIONSHIP 143 



kernel. It is, however, known from the observations of the 

 Messrs. Layard in New Caledonia that a small crow and different 

 species of parrots feed on the seeds of Erythrina, and they may 

 aid in the local dispersal {Ibis, vol. 6, 1882). 



To admit man's agency in carrying to Hawaii the seeds of a 

 tree which is only useful in supplying him with light wood for his 

 outriggers and his fishing-net floats would compel us to place in 

 the same category a great number of plants in some way useful 

 to him which are recognised as indigenous. The Polynesian 

 ransacks the vegetable world for his wants, and carries with him 

 in his migrations only his food-plants and the seeds of his sacred 

 trees. 



There remains then the possibility that the parent species, 

 Erythrina indica, was once in Hawaii but has since disappeared. 

 In order to establish this, it will be requisite to show not only 

 that the extinction of a shore-plant is probable, but also to 

 explain why the new species has selected such arid inland 

 localities for its stations, to account for the loss of buoyancy of the 

 seeds, and, if possible, to give an instance of the production of a 

 new species of Erythrina in a small isolated oceanic island. 



A study of the special circumstances of Hawaii leads one to 

 conclude that a shore-tree may become extinct in one of two ways. 

 It may be exterminated by insect pests, or it may be forced inland 

 through unsuitable coast-conditions and there be lost in the 

 resulting new species. One characteristic shore-tree, Cordia 

 subcordata, has indeed been almost exterminated by insects, 

 and even Erythrina monosperma is now from the same cause 

 on its road to extinction (see Note 53); but there is no 

 indication of their leaving modified descendants behind that 

 are pest-proof. The most probable view then is that the littoral 

 tree, having been driven inland through the unsuitability of the 

 coast-conditions, such as lack of beaches or want of moisture, has 

 there become modified. This is what has really happened, as I 

 have shown, with Caesalpinia bonducella in Hawaii. As indicated 

 in Chapter XVII., this characteristic beach-plant has here been 

 driven off the beach. There would thus be no difficulty in 

 assigning a reason why a littoral tree like Erythrina indica 

 should select arid localities when it extends inland, since, as is 

 pointed out in Chapter IV. and in other parts of this work, the 

 plants of the beach and of the arid inland district possess the same 

 xerophilous habit. 



With regard to the loss of buoyancy of the seeds in the case of 



