TRANSACTIONS OF WAGNER 
32 VEGETATION OF SOUTH FLORIDA 
lantic coast from Cape Hatteras southward, there is a southward-setting cur- 
rent,* which makes a gradual drift of silicious sand all the way down to Cape 
Florida. Hence it comes about that the sands fill in on the northern side of 
the inlet, and force the exit waters continually to widen the opening on their 
south banks, a process which causes the inlets to move down the coast. 
South of Cape Florida, Soldier Key begins the chain of Florida keys, where 
the coral beaches of calcareous sand take the place of the silicious sand beaches 
that extend north to Cape Cod. High dunes are characteristic of that part 
of Florida about Jupiter Inlet, where the wind-blown sand is silicious. Low 
dunes, or none at all, are characteristic of the coral beaches, because the cal- 
careous sand lends itself to rapid solution by rain water and later the grains 
may become rapidly consolidated into a tolerably firm mass, or rock. 
These coastal islands are separated by a number of inlets, which, be- 
ginning with Indian River Inlet, are from north to south St. Lucie Inlet, 
Jupiter Inlet, Lake Worth Inlet, Hillsboro Inlet, Ft. Lauderdale Inlet. 
South of Cape Florida, where the coral beaches of the keys are found, the 
passageways between the several islands are not designated on the coast map, 
but the keys which concern this phytogeographic study are from north to 
south Virginia Key, Key Biscayne, Soldier Key, Ragged keys, Sand Key, 
Elliott Key, Old Rhodes Key, and Key Largo. 
The keys, which are considered only incidentally in this monograph, are 
divided into four groups: The first group, called by Smallf the Upper Sand 
keys, comprise Virginia Key and Key Biscayne, of silicious sand. The second 
group, or Upper keys, consist of the keys that extend from Soldier Key to the 
West Summerland, or Spanish Harbor keys. They consist fundamentally 
of Key Largo limestone, and in the higher keys, dense hammocks are found. 
They are of younger coral rock than the Lower keys, which consist funda- 
mentally of Miami-Key West oölite, which forms the basic rock of the 
ancient Miami keys, which are a part of the mainland. The fourth group of 
the Lower Sand keys are composed of sand. They extend from the west- 
ward of Key West out into the Gulf of Mexico, and their vegetation has been 
investigated by Millspaugh. 
* Cf. Shaler, N. S.: Beaches and Tidal Marshes of the Atlantic Coast. Physiographic 
Processes, 1: 153. 
t Small, John K.: Flora of the Florida Keys, р. iii. 
f Millspaugh, Charles F.: Flora of the Sand Keys of Florida. Botanical Series, Field 
Columbian Museum, ü, No. 5, Feb., 1907. 
44. 
