450 NOTES ON THE FLORA OF SOUTHERN FLORIDA. 
part on the continental coast of the Gulf, and may as probably ” 
have reached the Keys from there as from Cuba. The most obvi- 
ous reason is found in the fact that the Bahamas are united with’ 
the Greater Antilles by innumerable islands and shoals, while on 
the contrary Florida and the Keys are separated from them by the 
Gulf Stream—a proof that ocean currents do not always serve to 
connect floral regions but at times aid in preserving the limits be- 
tween creations originally distinct.” Now to these suggestions 
some objections may be made. When we see the habitat of many 
hundred of species indicated in the books by the phrases “ New 
England to Florida,” “ S. Carolina to Florida,” etc., it seems evi- 
dent that the flora of Florida belongs to that of North America. 
But “Florida” in most of these cases means Northern Florida. 
Southern Florida, from Tampa Bay southward, has been explored 
only at solitary points upon the coast by a few botanists, who 
have taken notice only of the more conspicuous and chiefly woody 
plants. It is not improbable that when the vegetation of this 
region is better known it will prove to be not so different from 
that of the Northern Bahamas as Prof. Grisebach now supposes. 
Geological causes cannot be excluded in botanico-geographical > 
investigations where recent causes are insufficient to explain facts. ; 
he coral formation of Southern Florida—if it be true that the 
lyps cannot live but in a certain depth of water—indicates oe 
slow subsidence of the land, and this movement may possibly — 
have preceded the upraising of the tertiary Atlantic and Gulf 
coast of the Southern States and the existence of the Gulf Stream. 
Between Bemini Point and Cape Florida the depth of the streat 
is considerably less than at any other point, and this may hee 
e line of connection between Florida and a tropic terk 
tory eastward, of which the Bahamas are the remnants. 
more probable that the “few” woody plants enumerated 
bach have immigrated across the channel or made the long @ 
of the shores of the Gulf, than that they are the residue of 40M 
larger number of plants common to Florida and the Bahamas- 
But is the number of these plants indeed so small? Dr. 
man enumerates in his “ Flora of the Southern States” no 
231 species which do not extend northward of Tampa Ba, 
these 16 may be added from other sources,* making 24 
*From DeCandolle’s Prodromus, Hyptis spicata, Croton humilis and lit 
rothamnta Fondiri, and Zante Pioridans m Bot. Mex. Bound: 
and pumila ; from Bot. 
