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FREE INSTITUTE OF SCIENCE 
VEGETATION OF SOUTH FLORIDA 
187 
The phanerophytic climate is characteristic of all tropic lands with a 
rainfall which is not so small that the vegetation is exposed to critical con- 
ditions on account of its absence. Examining our table, we find that in the 
large percentage of phanerophytes, the region of tropic Florida belongs in part 
at least to a phanerophytic climate, but it is not typic, as the percentages of 
hemicryptophytes, therophytes and chamephytes are also large and in that 
respect the two regions of South Florida approach more closely the normal 
spectrum of Raunkizr. 
EVOLUTION OF PLANT FORMATIONS 
The history of the vegetation of South Florida may be traced best by 
beginning with the period of elevation when the Miami-Key West oólite was 
raised to its present level as an area of dry land. The limestone composing 
the Miami-Key West deposits soon weathered into a thin superficial soil which 
was early tenanted by the slash-pine, Pinus caribaea Morelet. The early 
occupancy of the oólite is evidenced by the fact that the slash-pine vegetation 
is found on some of the Lower keys, beginning with No Name Key and Little 
Pine Key and extending westward for a distance of 48 kilometers (30 miles) 
under similar edaphic conditions on the Miami-Key West oólitic limestone of 
which these islands consist. The presence of such slash-pine vegetation on 
these keys isolated by a considerable distance from the mainland oólite is 
evidence that these two widely separated areas of limestone were elevated at 
the same time and later were invaded by slash-pine vegetation which has re- 
mained in undisputed possession of the oölitic limestone deposits. ‘The Upper 
keys, consisting of Key Largo limestone, were elevated subsequently, and at a 
time when hammock vegetation invaded the region, so that to-day hammocks 
are typic of the Key Largo limestone except the flat borders of such keys 
where the mangrove swamps are in evidence. This differential elevation of 
the two kinds of limestone indicates that hammock vegetation followed the 
pine vegetation in the occupancy of the Florida keys, and on the peninsular- 
mainland the same succession has probably been the course of events. De- 
tached islands of slash-pine forest probably existed at the same time on the 
higher ground of southwest Florida, as far north asthe Caloosahatchee River. 
The high land north of the Caloosahatchee River connected with the mainland 
farther north was elevated earlier than the Miami-Key West oólite, and at the 
