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. ı 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 Atlanticand 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 Smith, Eugene A.: loc. cit., p. 203. 
