250 PLANTS, SEEDS, AND CURRENTS 



Pear Cay and Eastern Cay, which are exposed to the full force of the 

 strong winds, the main stem lies prone and roots in the sand, only the 

 primary branches rising erect into the air (see Note 3 of the Appendix). 



From Mr. Lansing's methodical examination of the Florida sand- 

 keys west of Key West, we are able to form an idea of the relative 

 abundance of Tournefortia gnaphalodes in comparison with the other 

 plants, the flora being almost entirely littoral and in many respects 

 identical with the shore flora of the Turks Islands. Of the nineteen 

 keys described, those occupied alone by mangrove colonies being 

 excluded, nine possessed this plant, which, though nowhere abundant, 

 is evidently fairly well distributed over this region. Yet, although 

 better represented than Sccevola Plumieri, which was found on only 

 four of the keys, in no single key did it form a predominant feature 

 of the vegetation. In five cases it was either scanty or very scanty, 

 and in the other keys it grew in moderate amount. 



From the data given by Grisebach, Harshberger, Millspaugh, 

 Urban, and others, it is evident that the currents have distributed 

 Tournefortia gnaphalodes all over the West Indian islands, both large 

 and small, from Cuba, Jamaica, and the Bahamas to Barbados 

 and St. Vincent. I have no information relating to its occurrence 

 on the mainland of South America; but its ability to establish 

 itself on the most isolated islands is indicated by its existence on 

 Grand Cayman and the Alacran Shoals (Millspaugh). Though most 

 characteristic of the vegetation bordering the sandy beaches, it is 

 frequently to be found on a rocky shore of calcareous formation. 

 It is a plant that prefers coasts fully exposed to wind and wave, 

 and I have shown in Note 3 of the Appendix how well it adapts its 

 growth to the wind-pressure. Dr. Millspaugh, who had an extensive 

 acquaintance with it in the West Indies, states that it prefers a 

 station " on the beach line facing the open sea " (Plant. TJtow.). 

 In this respect it resembles T. argentea its sister species of the Pacific 

 islands, both plants on account of their hardy nature being amongst 

 the first shrubs to establish themselves on a newly formed coral-sand 

 key. 



Some of the results of the foregoing comparison of these two 

 shore species of Tournefortia are tabulated in the table on p. 251. 



Vigna luteola, Benth. 



In my volume on Plant Dispersal I deal with Vigna lutea, A. Gray, 

 a common strand species in the tropics of both hemispheres, but, 

 as it would appear, most characteristic of the Old World. I was 

 familiar with it amongst the beach plants of Hawaii and Fiji. Its 

 small seeds, 5 or 6 mm. long, were frequent in the beach-drift of those 

 groups, and also in the floating drift of Fijian rivers. Experiments 

 showed that they can float for months unharmed in sea- water. 



Widely spread in the warm parts of the New World is a sister 

 species, Vigna luteola, Benth. In its littoral station, in its general 

 habit, and in the buoyancy of its seeds, its behaviour is similar to 

 the other species. It has a very wide distribution in the New World. 

 According to Hemsley and Grisebach, it ranges from Carolina and 



