THE BAHAMA ISLANDS 215 



which the heat, salt, and wind are resisted and the difficulties of living solved ; 

 but some of the most noticeable may be referred to. The beach plants are 

 particularly liable to be uprooted or buried by the shifting sand, and to meet 

 this danger they are nearly always furnished with vegetative means of propa- 

 gation, either by underground rhizomes (many grasses, as Uniola, Sporo- 

 bolus), prostrate creeping branches which root at the nodes (Ambrosia his- 

 pida Pursh, Distichlis maritima Eaf.), or recurved branches which root at 

 their tips (Tournefortia, Sccevola}. Plate XLIV, Fig. 1, illustrates this 

 habit. If one part is covered or uprooted another may continue the growth. 

 Beach plants are also apt to have more or less succulent leaves, which are 

 either polished or reflect the intense light (Borrichia glabra Small, Sccevola), 

 or hairy, to prevent too rapid evaporation (Borrichia argentea DC., Tourne- 

 fortia), or the leaves may be hard, narrow, and inrolled (many grasses and 

 sedges, Rhacicattis, Suriana, Jacquinia). The epidermis is generally very 

 thick and the stomata are protected in various ways. 



The scrubby coppice growth that makes up the greater part of the vege- 

 tation contains remarkably few succulent plants. There are no yuccas, few 

 cacti, and but one species of agave. 



The conditions, however, are generally arid; the porous rock drains 

 quickly and there are often periods of excessive drought. The leaves are as 

 a rule hard, and grayish in color from the presence of hairs or wax. In 

 many species the young leaves hang vertically and are protected by rusty 

 hairs. In Langeria densiflora (Griseb.) B. & H., a tree found on New Provi- 

 dence, the young leaves are coated with a kind of lacquer which, in dry weather, 

 becomes very hard, and effectually prevents evaporation. 



The plants of salt marshes and mangrove swamps possess many inter- 

 esting and peculiar adaptations. In the case of Rliizophora mangle L. (Plate 

 XLI, Fig. 1, and Plate LXXXIV, Fig. 2) the old leaves become much 

 thicker and change their function from photosynthesis to water storage. The 

 adventitious roots descend from the branches and, taking hold of the mud, 

 extend the plant indefinitely. The fruits of this species germinate on the 

 tree and are for a long time nourished by the parent plant. When they 

 finally fall they float in the water root downwards, and on coming in contact 

 with the bottom send out with remarkable rapidity the young roots that had 

 already started to grow beneath the epidermis. Avicennia nitida Jacq., another 

 mangrove plant, sends up from its underground roots others that rise per- 

 pendicularly out of the ground for a foot or more. These aerial roots, as 



