FREE INSTITUTE OF SCIENCE 



VEGETATION OF SOUTH FLORIDA 



and will not germinate in dense shade." Without contradicting either of 

 these points of view, it seems to the writer that a slightly different inter- 

 pretation of the facts can be made. Bessey's theory accounts for the genesis 

 of hammocks only in part; Harper's theory for the sharp demarcation of 

 pineland, on the one hand, and the hammocks on the other, and it accounts 

 in part for the preservation of the moister hammock land and its climax 

 vegetation, once the genesis of it is explained. Bessey starts with the ap- 

 pearance of non-coniferous species in a closed formation of pineland vegeta- 

 tion, but he does not explain fully how such plants were able to get a start 

 in a closed formation in competition with the pine barren vegetation, which 

 is a remarkably exclusive and persistent type. My theory, that the ham- 

 mocks started in depressions with a sandy-loamy, perhaps marly, soil and 

 under different edaphic conditions, explains why non-coniferous species 

 have been able to invade the pineland and overcome the competition of 

 well-established and exclusive pine vegetation. The broad-leaved trees and 

 shrubs are able to get hold in the banana holes, because the different edaphic 

 conditions of limestone, pot-hole environment have excluded the typic pine 

 barren plants. (Plate III, Figs, i and 2.) 



These different edaphic conditions are one of the results of the natural 

 relations of the limestone and the surface beds of sand and loam which have 

 been deposited over it. A central divide, or water-shed, 60 to 75 meters in 

 elevation, is found with numerous ponds in the central part of the state be- 

 tween the Atlantic and Gulf drainage systems. On either side of this water- 

 shed erosion has removed the sands and partially exposed the underlying 

 limestone, and wherever this rock, in its disintegration, affects the over- 

 lying limestone, sands and soils, the conditions are found for the formation 

 of hammocks, which have soils that represent the interaction of sand, loam, 

 and decomposed limestone which are marled in their formation.* 



It will thus be seen that the distribution of the hammocks depends upon 

 two factors: First the configuration of the underlying limestone, with its worn 

 surface, its elevations and depressions, and second, the position of existing 

 lines, or channels of drainage. After the typic species of the banana holes 

 have become established in the depressions that are widely spread through 

 the pineland, the subsequent course of events is much as Bessey has so 

 lucidly described. Harper's fire theory, although perhaps applicable to 

 'Consult Smilh, Eugene A, : loc. cit., p. 203. 



