THE BAHAMA ISLANDS . 217 



1. The Ipomea pes-caprce Association. — Here the Ipomea itself is by no 

 means abundant, occurring only rarely at considerable intervals, but the 

 association corresponds to the Ipomea association of other tropical shores. At 

 points where the Ipomea does not occur, its place is taken by the grasses, 

 Paspalum vaginatum Sw. and Sporoholus virginicus Kunth. This grass strip 

 varies in width from 1 to 10 feet, beginning at high water mark and running 

 back the greatest distance where the next association is broken. The two 

 grasses occurring here are both good sand-binders. Paspalum has thick 

 trailing branches with leaves in tufts at the nodes, while Sporoholus has 

 underground runners with closely tufted upright branches (Plate XLVII, 

 Fig. 1). 



2. The Uniola-Tournefortia Association, following the above, occupies 

 the gently sloping, or in some places quite level, sandy strip that extends to the 

 scrubby coppice behind. At the point where these observations were taken its 

 width was from 3 to 12 feet. JJniola paniculata L. is not present at all points, 

 but is scattered at intervals, sometimes in dense, pure growth, but frequently 

 more open. Where the Uniola is absent, or scattered, its place is taken by 

 large clumps of Tournefortia gnaphalodes E. Br. and Scoivola plumieri L. 

 mixed with Suriana maritima L., Salmea petrohioides Griseb., Strumpfia 

 maritima Jacq., and a little Borrichia glabra Small (or B. argentea DC). 

 The aromatic Ambrosia hispida Pursh occupies open spots in this association 

 and penetrates more or less into the scrub behind. Its prostrate branches 

 are often 10 or 12 feet in length, with upright shoots reaching a height of 

 6 to 12 inches. Sesuvium portulacastrum L. occurs here also, but is not so 

 abundant as Ambrosia. Its fleshy procumbent stems reach a length of 6 

 feet, and from every node are produced short lateral branches of a rather 

 definite length. These also lie flat, except at the tips, which are turned up- 

 ward, but they rarely root and may be characterized as " kurtztriebe." The 

 main stems do not take root at every node but only at intervals of about 2 feet. 



3. Pithecolohium-Salmea Association. — This begins immediately behind 

 the association last mentioned. Its principal plants are PHhecolohivm 

 keyense Britton (Eam's horn), Salmea petrohioides Griseb., Torruhia longi- 

 folia (Heimerl) Britton (Blolly), Jacquemontia jamaicensis (Jacq.) Hall, 

 Erithalis fruticosa L. (Black torch), Lantana involucrata Sw. (White lantana), 

 Ernodea Jittoralis Sw., and Solanum hahamense L. (here without spines on 

 the leaves), with an occasional tuft of Cyperus hrunneus Sw. The scrubs of 

 this formation are low and dwarfed, generally not more than 3 feet high. They 



