228 FLORIDA GEOLOGICAL SURVEY-THIRD ANNUAL REPORT.
which however has no connection with the Pliocene clay of northern Florida. The same rock extends out into the southern part of the Everglades to an undetermined distance.
Strange to say, the Miami limestone, unlike nearly all other limestones, seems to have very little effect on vegetation. The drier parts of it are covered with forests of pine (Pinus Caribao,'n) with a dense undergrowth of saw-palmetto, essentially similar in aspect to the forests of the southern part of the South Florida flatwoods; and the parts subject to occasional inundation are treeless, like the prairies in the region just named. The upland forest. sometimes known as the Biscayne pineland, which has a maximum width of about ten miles, is dotted with hammocks varying in extent from one to several hundred acres, in which the trees are nearly all of tropical species, but probably not necessarily lime-loving.
The water-level in the Everglades fluctuates considerably witt the seasons, so that there are large areas around the edges which are dry in spring and inundated in fall, like the ponds and shallow lakes of northern Florida.* In this part, however, there ace many depressions which are permanently wet, and peat accumulates in these in the same way as in the deeper holes in the prairies of the Middle Florida hammock region. Some estuarine peat is also) found along the Miami River and other streams.
Analyses of peat from this region will be found under localities 24 to 27.
COAST PRAIRIE.
Bordering the Biscayne pineland from Cocoanut Grove soltihwestward, and extending all the way to the coast, which is nowhere more than ten or twelve miles away, is a flat prairie so slightly elevated above the sea that it must be inundated by salt water in times of storms or exceptionally high tides. It is dotted with clumps of bushes and small trees like the southern part of the Everglades, and by some botanists it has been considered a part of the Everglades. There are various minor differences in vegetatioil between the coast prairie and the Everglades, however, (as might be expected from their different relations to salt water), and one very marked difference in aspect. Everywhere in the coast prairie except within a mile or two of the pine land there are millions of
*For. a popular account of some explorations at the south end of the Everglades in the dry season, with references to some earlier literature on the same region, see Florida Review (Jacksonville) 4 :44-55, 147-157. July andl August, 19IO.