1920 | THe Lanp or FERNS 93 
careous sand, active along the coast, wietionary back of the coastal 
lagoons and in the interior. Sheli-mounds or kitchen-middens are 
usually built on or near dunes. The so-called ‘‘serub,’’ which com- 
prises extensive areas of white sand supporting a characteristic plant 
association, is ineluded here. 
In these various areas are found about one-third of the different 
kinds of ferns and fern-allies growing naturally in all America north 
of Mexico; and the variety in habit and leaf-form of these far exceeds 
that exhibited by the ferns of any other part of either the United 
States or Canada. In Florida more than one hundred ferns and fern- 
allies, both simple and complex, from very small to gigantic, grow 
either as native or as naturalized plants. 
There are ferns in nearly every part of the State, but only the more 
“marked areas of distribution will be referred to on the following 
pages, to-wit: northern Florida is the long horizontal (east-west) axis 
of the State, while peninsular Florida is the long perpendicular 
(north-south) axis. The Florida Keys$ are the islands of the Florida 
reef off the southern coast. The Everglade Keys are islands in the 
southern part of the Everglades. The Florida Keys and Everglade 
Keys are islands of rock. The upper series of Florida Keys are of 
coral limestone and are clothed with hammock. The Everglade Keys 
and the lower series of Florida Keys are of dolitic limestone and are 
clothed with both hammock and pine forest. The lime-sink region is 
an area in the northwestern part of the peninsula, which is surrounded 
by other phytogeographic regions. It comprises mostly rolling sandy 
Pine woods with depressions or sinks, but only few streams. How- 
ever, near the rivers there are many large springs. 
The different kinds of fernworts may be grouped thus: (a) natur- 
alized exotic species, (b) endemic species, (¢) species typically of a 
more northern distribution, and (d) species typically of more south- 
€rn distribution, and consequently tropical. 
There are, apparently, only three naturalized fernworts. These 
are: 
Pyenadoria longifolia (Bracken) 
Dryopteris setigera (Wood-fern) 
Marsilea vestita (Pepperwort) 
