1920 | THe LaNnp or FERNS 99 
dence of reduction are not hard to observe. These islands have been 
worn down and washed away not only by the never-ceasing action of 
the sea, but also by the hurricanes of ages. This is quite evident. 
The rock surface, particularly in the ease of the Lower Keys whose 
limestone corresponds to that of the Everglade Keys, is polished off 
and plate-like, instead of merely leached out and honeyeombed. What 
the former fernworts consisted of we cannot even imagine, but we are 
safe in assuming that the list was more extensive than that which we 
are able to record there now. 
The Everglade Keys, the second tropical area—a phytogeographic 
region isolated in the Everglades—comprise a curved series of lime- 
stone islands appearing on the surface about the neighborhood of the 
Miami River, trending southwest and disappearing in the southern 
end of the Everglades. The area is surrounded by the Everglades, 
except where a portion fronts on Bay Biscayne or its lagoons. | 
As on the Florida Keys, the native flora of the Everglade Keys 
consists almost wholly of tropical plants. Pineland predominates 
in extent of area today; but the few hammocks—evidently themselves 
remnants of a once dominant and magnificent forest—still harbor 
nearly fifty kinds of our tropical ferns. And among these are no 
naturalized exotic species, no typically northern species. The only 
northern ferns in the vicinity are those occurring where the Ever- 
glades and the limestone islands meet. 
The number of ferns and fern-allies in this region is quite re- 
markable when we consider that the area involved comprises only a 
few hundred square miles, a mere fraction of the State’s large area. 
Although variety in soil and other, physical features is slight, this 
area harbors more than fifty per cent. of the fern flora of Florida. 
An overwhelming majority of the species are typically tropical 
American. In addition to these, there are several cosmopolitan spe- 
cies and a few endemic ferns. The plants of nearly one-third of the 
Species are epiphytic, living on the moisture of the air and getting 
Solid food from the bark and small quantities of humus, while an- 
chored on trees and prostrate logs. This condition doubtless makes up 
to some extent for,the lack of variety in topography, climate, and soil. 
The Everglade Keys consist of two main divisions, the Biscayne 
Pineland11 and the Long Key pineland. The former group is made 
Haan reaches of an ped river that flows southward and empties into the Bay of 
orida. The larger or eastern group of islands takes its name from Bay Biscayne which 
Washes t¢ es of one of the islands for a distance of about fifteen miles. e smaller 
e shor 
Sie lanes its name from Long Key, the largest island lying west of the sloughs referred 
e. 
