XV LITTORAL AND INLAND PLANTS' RELATIONSHIP 149 



The whole problem of the dispersal of Sophora was brought 

 immediately to my notice at Corral, in latitude 40° S. on the coast 

 of Chile. Here a small tree of the section Edwardsia was growing 

 in fruit on the lower slopes of the hills, becoming bushy when 

 descending to the beach. Specimens of its four-winged pods have 

 been identified at the Kew Museum as those of Sophora tetra- 

 ptera ; and, as far as the pod is concerned, I cannot distinguish 

 between my specimens of the Hawaiian S. chrysophylla and the 

 Chilian species. Subsequently I found the buoyant seeds of the 

 same plant amongst the stranded beach-drift at Bahia San 

 Vincente, nearly 200 miles further north. This led to my experi- 

 menting on the capacity of the plant for dispersal by the currents, 

 and as a result it was ascertained (see Note 56) that whilst, as in 

 the case of S. chrysophylla, the pods floated only one or two weeks, 

 the seeds on account of their buoyant kernels floated for several 

 months in sea-water, retaining their power of germination. The 

 Chilian plant thus differs significantly in its capacity for dispersal 

 by currents from the Hawaiian species, the seeds of which sink in 

 sea-water even after years of drying. 



The Mamani tree in Hawaii had always been an object of great 

 interest to me. I was attracted by the mystery surrounding its 

 origin and had long suspected that the clue was to be found in the 

 non-buoyancy of its seeds and in the absence of a littoral species 

 of the genus. When in Fiji it was to the littoral Sophora 

 tomentosa that I looked in vain for a solution of the riddle, and 

 seven years afterwards on the coast of Chile a solution of this 

 enigma of the Hawaiian mountains presented itself in the form of 

 an argument somewhat in this shape. 



On account of the elevated station of the Mamani tree 

 (S. chrysophylla) in Hawaii it is to be inferred that the original 

 species was a plant of the temperate regions or of the uplands 

 of some tropical mountains. If it has had its origin in some 

 shore-plant dispersed by the currents, that species can only now be 

 found on the coasts of extra-tropical regions. Such a maritime 

 plant had buoyant seeds ; and plants of this type are presented by 

 Sophora tetraptera and its allied species that are at home in the 

 cool latitudes of the southern hemisphere, as in Chile and New 

 Zealand. No difficulty, as I argued, could be connected with the 

 loss of buoyancy of the seeds of the Hawaiian mountain species, 

 since it follows the general principle (laid down in Chapter II.) that 

 in the same genus coast species have buoyant seeds or fruits, and 

 inland species those that sink ; and in support of this view it was 



