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 fight 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." He 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. 104106. 

 t Spencer, J. W., " Becon struct ion of Antillean Continent," pp. 128 

 129. 



