TRANSACTIONS OF WAGNER 

 104 



VEGETATION OF SOUTH FLORIDA 



at the edge of the pineland in South Florida near Detroit were found two ham- 

 mocks, one about ten ares in extent, the other occupying about one hectare. 

 The smaller occupied a basin-shaped depression, the center of which was filled 

 with water. The larger hammock was somewhat more elevated and level with 

 a deep, rich soil. No sharp demarcation was found in the vegetation of the 

 smaller hammock, which filled a sink hole, and the larger drier one. 



E. A. Bessey* has advanced the theory that "Somewhere in the pine 

 woods a few of the small shrubs, or occasional small persimmons (Diospyros 

 virginiana L.), or other broad-leaved trees of which a few kinds are formed 

 also in the pine woods, form a somewhat sheltered place within which the 

 air is somewhat moister. Here owing to the increased shade, the soil does 

 not dry out so much, as where the sun is more direct. Other trees, favored 

 by this increased moisture of soil and air, especially the live-oak, are thus 

 enabled to get a start. Soon more trees and shrubs appear, the conditions 

 becoming more favorable the more numerous and larger they become. The 

 whole space between the trees grows up to underbrush. The denser the 

 growth becomes, and the larger the trees, the more humid is the air, while 

 the dense shade protects the soil from drying out. Many of the plants, that 

 in the open pine forest are small shrubs, become fair-sized trees when they 

 encounter these more favorable conditions. The denser the growth, the 

 more humid the air and the moister the soil, so much more fully do these and 

 other typical hammock plants reach their full development. Soon epiphytes 

 begin to appear, other typical hammock plants come in and we have a 

 typical hammock." Harper f believes that the origin of a hammock in a 

 certain area can be traced directly to the protection of that area from fires 

 that sweep the adjacent unprotected pinelands. He says: "for the Florida 

 hammock peninsulas, if not for all other cases referred to, the key to the 

 situation can be expressed in a single word: Fire. On this theory it is 

 easy to account for the origin of insular and peninsular hammocks. The 

 absence of fire would in time allow sufficient humus from the pioneer vegeta- 

 tion to accumulate to give the hardwoods a start, and the latter would 

 grow up and finally make enough shade to prevent the reproduction of the 

 pines and other pioneer plants, which are what foresters term 'intolerant' 



* Bessey, E. A.: The Hammocks and Everglades of Southern Florida. The Plant World 14: 

 271-273. 



\ Harper, Roland M.: The Relation of Climax Vegetation to Islands and Peninsulas. Bul- 

 letin Torrey Botanical Club 38: 522-523, 19 n. 



