FREE INSTITUTE OF SCIENCE 



'79 



VEGETATION OF SOUTH FLORIDA 



the pine forest. At another place beyond Detroit, a hammock touches the 

 open prairie with its sclerophyllous vegetation (Text Figure i). The prairie 

 is dotted with islands of bushes and low trees and Small considers it to be 

 a part of the Everglades. There are differences, however, which lead one to 

 consider the coastal prairie a distinct phytogeographic formation. The coastal 

 prairie is influenced by salt water. Several miles south of the pineland, the 

 surface of the prairie is sprinkled with low mangrove bushes, Rhizophora 

 mangle L., raised on stilt-like roots and with round-headed tops of light-green 

 foliage, and the presence of this tree phytogeographically makes the coastal 

 prairie a formation distinct from the Everglades proper (Plate II, Fig. i). 



As the botanist approaches the coast of the Bay of Florida, where the rail- 

 road leaves the mainland for the Florida keys, the red-mangrove trees become 

 larger and more closely set together until when the shore is reached they form 

 a continuous fringe along the coast. From the tests made of Miami River 

 water with the hydrometer in the midst of the mangrove vegetation, it would 

 appear that the red-mangrove will grow in fresh water, hence it is not fresh 

 water that reduces its size in the coastal prairie. Here it is surrounded with 

 the saw-grass and other grasses that form a close sod or compact root system, 

 the mangrove is finally suppressed, when the prairie vegetation becomes 

 absolutely dominant. It would appear that with the advance of the southern 

 coast of Florida by the encroachment of the mangroves upon the shallow bays 

 the prairie vegetation follows the advance of the mangroves in natural suc- 

 cession, and as rapidly as the prairie conditions prevail the mangrove trees 

 become reduced in size and finally are suppressed.* Some of the hammocks 

 scattered over the prairie have such component species as tall palmettos, 

 Sabal palmetto (Walt.) R. & S., waxberry, Cerothamnus (Myrica) ceriferus 

 (L.) Small. At the southern end of the prairie, the surface is intersected by 

 channels of water and the prairie islands are replaced by mangrove-covered 

 islands. 



The plants collected by the writer on the coastal prairie at Detroit are 

 scattered over the surface and are not found in pure association. It is by this 

 commingling of species that the surface soil is covered by a dense mass of 

 the following plants: 



* Harper suggests that the succession may be in the other direction, viz., the invasion of the 

 prairie by mangrove trees. 



