VEGETATION OF FLORIDA 
169 
A West Indian fauna, too, is associated with the flora in this 
portion of the United States, as will be shown later on. The 
problem presented by the origin of this tropical element in 
the North American flora at any rate is not quite so simple 
as it appears at first- sight. Dr. Harshberger is of the opinion 
that the hummock lands on which the tropical flora principally 
grows represent part of an ancient system of islands which 
existed at a time when the Gulf Stream passed right across 
the then submerged portion of northern Florida. We might, 
therefore, make further enquiries as to whether this theory is 
supported by geological or other evidence, before taking for 
granted that the tropical element in the fauna and flora of 
Florida is of purely accidental origin. 
Professor Shaler * informs us that along the coast of 
Florida, both on the eastern or Atlantic and the western or 
Gulf side, there arise from beneath the sea a number of 
submarine springs. They thus discharge great tides of fresh 
water, originally gathered on the land, through openings on 
the floor of the ocean. He argues that these springs probably 
shed their waters along the margin of the sea above high water 
level, and remarks, “ I cannot conceive any such under¬ 
ground waterways to have been produced under the existing 
conditions of land and water.” lie assumes consequently, that 
Florida, or a certain part of it at any rate, must have stood 
at a higher level in relation to the sea than it does now within 
comparatively recent geological times. 
Through the discovery of a submerged system of drainage- 
valleys off the coasts of Florida and the Antilles, Dr. 
Spencer is led to believe in an elevation of this area during 
the earlier part of the Pleistocene Period to the extent of 
8,000 to 12,000 feet or more. During a subsidence which 
followed, according to the same author, the greater part of 
the existing peninsula of Florida was submerged. Dr. 
Spencer f does not specify what parts of it remained above 
water, but presumably the whole of the southern Florida 
which is low-lying was included in the submerged portion. If 
* Shaler, N. S., “ Nature and Man in America,” pp. 104—106. 
t Spencer, J. W., “ Eeconstruciion of Antillean Continent,” pp. 128 — 
129. 
