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VEGETATION OF SOUTH FLORIDA 



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 chamasphytes are also large and in that 

 respect the two regions of South Florida approach more closely the normal 

 spectrum of Raunkiaer. 



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 oolite 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 oolite 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 oolitic limestone of 

 which these islands consist. The presence of such slash-pine vegetation on 

 these keys isolated by a considerable distance from the mainland oolite 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 oolitic 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 as the Caloosahatchee River. 

 The high land north of the Caloosahatchee River connected with the mainland 

 farther north was elevated earlier than the Miami- Key West oolite, and at the 



