218 VEGETATION 



occupy the outer slope of the low ridge of wind-blown sand that skirts the 

 shore. As the crest of this ridge is approached, the sand becomes mixed with 

 a little more humus and there is a rather sudden transition into the higher 

 growth of the next association. 



4. Erithalis-Reynosia (or littoral sand-co.ppice) Association. This occu- 

 pies the flat top, not often over 12 or 15 feet wide, of the sand ridge just men- 

 tioned, and the growth averages about 8 feet, rarely reaching 12 feet in height. 

 Most of the plants mentioned in this last association occur here also, but the 

 principal constituents are ErithaUs fruticosa L. (Black torch), Reynosia sep~ 

 tentrionalis Urban (Darling plum), Metopium metopium (L.) Small (Poison- 

 wood), Torrubia long if alia (Heimerl) Britton (Blolly), 8almea petrobioides 

 Griseb., Rapanea guianensis" Aubl. (Beef -wood), and Ilex krugiana Loes. 

 Genipa clusicefolia, Griseb., Acacia choriophylla Benth. (Cinnecord), Bumelia 

 loranthifolia (Pierre) Britton (Milk plum), Bourreria havanensis (L.) Miers 

 (Strong back), Bumelia microphylla Griseb. (Ink-berry), and Uniola racemi- 

 flora Trin. are less commonjy present. 



5. The Silver Palm Association covers the inner slope of the ridge and 

 extends to the edge of the marshy depression behind. As the name implies, 

 the silver palm is the character growth here. Its height varies from 8 to 14 

 feet and it is by far the most conspicuous plant of this area. Of the under- 

 growth, Uniola racemiflora Trin. is most abundant. Mixed with it are dwarf 

 specimens of Pithecolobium keyense Britton, Torrubia longifolia (Heimerl) 

 Britton, Salmea petrobioides Griseb., ErithaUs fruticosa L., Rapanea guian- 

 ensis Aubl., Bourreria havanensis (L.) Miers, Lantana involucrata Sw., Erno- 

 dea littoralis Sw., Corchorus hirsutus L., Reynosia septentrionalis Urban, 

 Cordia bahamensis Urban, and Metopium metopium (L.) Small. 



FRESH-MARSH FORMATION. This occupies a long depression behind the 

 beach where the soil is saturated or entirely covered with shallow water. Thatch 

 palms (Inodes palmetto (Walt.) Cook) are abundant on the damp margins 

 of the marsh and a few also penetrate into the shallow water. Cladium effu- 

 sum Torr., Willughbwya heterophylla Small, Centella repanda (Pers.) Small, 

 the attractive, white-flowered Sabbatia companulata (L.) Britton and Ipomea 

 sagittata Cav., with large purple flowers, are also common as marginal plants. 

 Further out large clumps of Anona palustris L. (Custard apple) appeared, 

 and a little Rhizophora mangle-Ij. (Mangrove) in deeper places gave evidence 

 that the water was not quite fresh. This formation is about one-half mile 

 wide and passes northward into the next. 



