FOREIGN DRIFT OF THE TURKS ISLANDS 139 



some influence that inhibits the establishment of Guilandina bonducella 

 as a littoral plant in these islands. As I found a few seedlings on 

 the beaches of Grand Turk, it is apparent that the excluding cause 

 comes into operation after this stage. It may be that goats and 

 other animals browse on the young plants, since the soft prickles 

 that grow on the stems and on the under surface of the foliage could 

 offer no protection, though when they harden in the older plants 

 such protection would be afforded. 



It is probable that the same cause which prevents this plant from 

 assuming its characteristic littoral station on the Turks Islands has 

 operated throughout the Bahamas, an archipelago to which this 

 small group geographically belongs. I did not find it included in 

 the manuscript of Britton's and Millspaugh's Flora of the Bahamas, 

 its place in those islands being taken by the allied species, Guilandina 

 bonduc, which grows in coastal thickets. Neither species was recorded 

 by Lansing in his thorough examination of the Florida keys (west 

 of Key West). It is also apparent that although the seeds must 

 often be stranded on the Bermudian islands, where several West 

 Indian shore plants have found a home, the plant has not succeeded 

 in establishing itself there, since General Lefroy's remark that it 

 has only once been found (Chall. Bot., II., 30, 129) would scarcely 

 justify us in considering it a successful colonist. On account of its 

 cosmopolitan distribution as a littoral plant in warm latitudes we 

 are apt to infer that it could make its home everywhere; but the 

 foregoing negative facts of its distribution will prevent us from 

 forming such a conclusion. 



In my book on Plant Dispersal (p. 192) it is stated that almost 

 without exception the seeds of littoral plants of C&salpinia bonducella 

 (Guilandina bonducella) in Fiji floated both in sea-water and in fresh- 

 water, whilst in Hawaii the seeds of the same species growing inland 

 all sank. (On consulting my Fijian note-books I find that out of 

 forty-seven seeds from three different coast localities all floated in 

 fresh- water.) I made some additional observations on these two 

 points in the West Indies, that is to say, on the relative buoyancy of 

 the seeds in fresh and salt water, and on the influence of an inland 

 station on the floating capacity. With regard to the first point it 

 may here be said that out of sixty- eight seeds obtained from plants 

 growing by the beach at Savanna-la-mar in Jamaica 75 per cent, 

 floated in fresh-water and 84 per cent, in sea- water. Of eighty seeds 

 from plants growing by the beach near St. George's in Grenada 

 95 per cent, floated in fresh-water and 98 in sea-water. Out of 

 fourteen seeds collected from the beach-drift near Seville in Jamaica 

 all floated in sea- water, but only twelve or 86 per cent, in fresh- water. 

 It is thus evident that in the West Indies not quite all of the seeds 

 of littoral plants float in sea- water, and that of those that are buoyant 

 in sea- water not quite all float in fresh- water. We should represent 

 a rough average result if we said that of a hundred seeds of plants 

 growing by the beach ninety float in sea-water and eighty in fresh- 

 water. 



Concerning the effect of an inland station on the buoyancy of the 

 seeds I found that of a hundred seeds gathered from plants growing 



