96 K. H. CAMBAGE. 



The problem has been carefully investigated over a very 

 large area by Dr. Guppy. In speaking of the limited results 

 obtained by testing the buoyancy in sea- water of a collec- 

 tion of seeds, he says that such results are sufficient, how- 

 ever, to illustrate the character of the sorting-process by 

 which in the course of ages the plants with buoyant seeds 

 or seed-vessels have been gathered at the coast. This is 

 indicated, he writes : — 



(1) "By the far greater proportion of species with buoyant 

 seeds and seed vessels amongst the shore plants than among the 

 inland plants. 



(2) By the circumstance that almost all the seeds or fruits that 

 float unharmed for long periods belong to shore plants. 



(3) By the fact that when a genus has both inland and littoral 

 species, the seeds or fruits of the coast species as a rule float for a 

 long time, whilst those of the inland species either sink at once 

 or float only for a short period." 1 



In regard to Acacia Farnesiana Dr. Guppy points out 

 (p. 559) that it was introduced to the Hawaiian Islands by 

 Europeans, and that pods of this species are now washed 

 up on the beaches of the west coast of Oahu, one of the 

 islands, and the seeds are to be seen germinating in num- 

 bers on the beach, the seedlings striking into the sand. 



He also writes : — "The pods float unharmed in sea- water 

 for four or five weeks, but the seeds, when freed, sink." 



Dr. F. Wood-Jones mentions that many hard seeds and 

 seed-pods are washed ashore on Oocos-Keeling Islands. 2 He 

 also has seen a tree come ashore from some far off land, 

 carrying quite a wheelbarrow-load of fine earth in its 

 buttressed trunk (p. 290). He adds: — " It is certain that 

 such a tree would have many tenants when it started on 



1 Observations of a Naturalist in the Pacific between 1S96 and 1899, 

 by H. 13. Guppy, m.b., f.r.s.e., Vol. n, Plant-Dispersal, p. 22, (1906). 



2 Coral and Atolls by F. Wood-Jones, b.sc, f.z.s., p. 171. 



