612 PROCEEDINGS OF THE ACADEMY OF [Sept., 



detritus, vary in size from an acre to many hundred acres, and are 

 scattered as islands in the everglades and pine forests instead of sur- 

 rounded by the ocean, as they formerly were before the sea bottom be- 

 tween them became dry land by elevation. The trees, shrubs and 

 woody vines harbor an almost incredible growth of plants of various 

 categories. The growth of epiphytes is especially striking, for in num- 

 erous cases the tree trunks and branches are completely clothed with 

 air plants, and so prolific are the orchids and bromeliads that many 

 individuals are forced to growth on the ground and on the neighboring 

 pine trees.' Here occur the great majority of flowering plants now 

 known to be common both to the West Indies and the mainland of 

 North America. As the rock of New Providence Island, of the Bahama 

 group, is essentially identical with that of the Florida south of Miami, 

 and as there are many trees and shrubs common to the two regions, as 

 well as to Cuba, while many species are endemic to each of the three 

 regions, we are forced to conclude from the evidence that the flora 

 gives that geologically and to a certain extent floristically the hummock- 

 lands formed originally part of the Antillean region. The hummock- 

 lands, perhaps, represent part of the ancient system of Keys which 

 existed at the time when the Gulf Stream left the American Mediter- 

 ranean through a channel which existed across the northern half of 

 Florida. It was when these islands formed an extended archipelago 

 coextensive with the Bahamas that the hummocks were occupied by 

 their present flora, which, therefore, shows the closest relationship to 

 that of the nearby Bahama islands. With the elevation of the land 

 through the epeirogenic movements of the earth's crust, through the 

 agency of coral polyps, vegetation, ocean and wind currents, the Gulf 

 Stream was directed into its present channel and the sea islands which 

 now exist in south Florida in the form of hummocks were connected 

 by dry land or by partially submerged banks to form the present 

 peninsula of Florida. 



With the appearance of level plains by the removal of the shallow 

 sea over a sandy bottom, the isolated trees and herbaceous plants 

 which associated together constitute the savanna formation appeared 

 and clothed the ground. Imperceptibly these savannas were trans- 

 formed by the appearance of trees into the pine-land formation. This 

 formation is characterized by a scattering growth of Pinus heterophyUa 



' Consult the articles by J. K. Small, and N. L. Britton, in Journal New York 

 Botanical Garden, III, No. 26, February, 1902; IV, No. 39, March, 1903; V, No. 

 51, March, 1904; V, No. 5.5. July, 1904; V, No. 56, August, 1904, to which the 

 writer is indebted for many facts herein set forth under the new cloak of general- 

 ization. 



