FOREIGN DRIFT OF THE TURKS ISLANDS 117 



of which by far the greater number are tropical South American. 

 But the endemism displayed in oceanic islands in the Indian and 

 Pacific oceans, as well as in the West Indian islands, is very remark- 

 able. The Mascarene Islands, Mauritius, the Andaman and Nicobar 

 groups, the Fijian, Samoan, and Tongan archipelagos, Cuba, Jamaica, 

 and even the Bahamas (Harshberger, p. 330), all hold one or two 

 peculiar species of Terminalia. If we were to look for the home of 

 Terminalia catappa in a region where the genus is best represented, 

 we should find it in the New World, particularly in South America. 

 The New World, we might imagine, ought to have been able to 

 provide its own wide-ranging littoral species; and it seems strange 

 that human agency should have had to intervene in the matter. 

 However, the distribution of the genus presents many problems 

 that cannot be dealt with here. 



Entada scandens, Benth. 



This plant is discussed at length in my two books, Plant Dispersal 

 and Studies in Seeds and Fruits. In the first named it is regarded 

 from the distribution standpoint. In the second, the germination 

 process, the various stages in the maturation of the seed, and the 

 development of its impermeability, are dealt with in much detail. 



The great floating powers of the seed have long been known, as 

 well as its ability to retain its germinative capacity after being 

 stranded on the European side of the Atlantic. The white, softish, 

 full-sized moist seeds of the green legume possess no buoyancy. This 

 capacity is acquired during the shrinking and hardening stage, being 

 due to the large cavity produced by the bending outwards of the 

 cotyledons as they dry, the materials of the typical dry seed having 

 no floating power. 



The initial buoyancy of the seeds when recently detached from the 

 plant is indicated by the results of experiments made in Fiji and 

 Ecuador (Plant Dispersal, p. 181), from which it is inferred that 

 quite 50 per cent, sink in sea-water and about 70 per cent, in fresh- 

 water. In a recent experiment made in Jamaica the proportion of 

 non-buoyant seeds in freshly gathered material was much smaller, 

 only 20 per cent, sinking in sea- water and 30 per cent, in fresh-water. 

 This variation in the initial buoyancy is due to the variation of the 

 conditions attending the shrinking and drying process, which would 

 probably be less complete in shady humid forests than in drier, 

 exposed situations. From curiosity I tested the buoyancy of a 

 hundred seeds with sound coverings that had been brought by 

 currents and stranded on the Turks Islands. Of these, all but five 

 floated in fresh-water and all but one in sea-water, the last named 

 having from some cause lost its buoyancy. In my previous work 

 on Seeds and Fruits it is shown that loss of impermeability may in 

 time be induced through some initial defect in the cuticle. 



The seeds form a frequent constituent of beach-drift in the warm 

 regions of the New World. Amongst localities in which I found them 

 may be mentioned Ecuador, both sides of the Isthmus of Panama, 

 Jamaica, and the Turks Islands, but not in Trinidad, Tobago, or 



