MISCELLANEOUS PLANTS 



239 



case, the xerophyte of the beach found conditions suited for xero- 

 philous plants in the dry inland districts ; whilst the fruits matured 

 and the seeds underwent the shrinking and hardening process under 

 somewhat similar circumstances in both stations. In the second 

 case, the xerophyte of the beach was placed under different climatic 

 and soil conditions in the lower forest zone. The fruits matured 

 and the seeds hardened in a moister climate, and we have seen 

 how the whole plant responded, since the inland plants were in 

 full leaf in the spring whilst those on the beach were leafless. 



The conclusion to be drawn from these experiments is, that whilst 

 the buoyancy of the seeds of littoral plants is retained when the same 

 plants grow inland, whether in moist or dry conditions, it is less 

 persistent when the inland plants grow in the humid conditions of 

 the lower woods than with those growing in plains or open- wooded 

 districts where drier xerophytic conditions prevail. The buoyancy 

 is retained, therefore, when the xerophytic conditions of the coast 

 are preserved in inland plains. It tends to disappear under the 

 moist conditions of the inland forests. We have here indicated 

 how it comes about that in a genus holding both littoral and inland 

 species the seeds or fruits of the former float and of the latter sink. 

 This is illustrated in the case of Sophora in the Pacific islands, where 

 the seeds of the wide-ranging shore species, S. tomentosa, float, and 

 those of the inland species, as exemplified by S. chrysophylla of the 

 Hawaiian forests, sink. 



It is probable that Sophora tetraptera, a tree of New Zealand and 

 South Chile, which grows at the coast but also grows inland, would 

 display buoyant seeds only when growing at or near the coast. 

 In an experiment on the seeds of the tree that I collected on the Chilian 

 coast it was found that half of the seeds floated in sea-water after 

 seven months' immersion. Two of them placed in soil germinated 

 and produced healthy plants. This is an extension of an experiment 

 described on p. 580 of my work on Plant Dispersal. 



A word may here be said about the source of Sophora tomentosa in 

 the New World. As far as the currents are concerned, it is far more 

 likely that its floating seeds reached Brazil by the short route in 

 the Main Equatorial Current from the Gulf of Guinea than that they 

 were carried in the Gulf Stream drift from the West Indies to Africa. 

 Yet the genus holding some thirty species is spread over the warmer 

 regions of both hemispheres. North America has its own species 

 that flourish in the prairie districts, in the North Mexican highlands, 

 and in the Rocky Mountains (Harshberger's Phyt. Surv. N. America). 



SURIANA MARITIMA, L. 



This shrub, the sole species of the genus, is one of the most widely 

 spread of tropical strand plants. It occurs in the Pacific islands, 

 on the northern coasts of Australia, in Malaya, in the islands of the 

 Indian Ocean, on the shores of the Asiatic mainland, on the East 

 Coast of Africa, but not, as far as I know, on the West Coast of that 

 continent, though its occurrence there is extremely probable. In 

 the New World it is widely spread over the West Indies, occurring 



