THE BUILDING OF THE LAND 17 



Florida is not so well known as is that of the 

 plants, but it is certain that we have many tropical 

 species of the former within our borders. I have 

 seen a large collection of butterflies made near 

 Havana and more than half of its species are also 

 Floridian. I do not know that any naturalist has 

 identified all our other insects. We have about 

 forty species of land and fresh-water mollusks in 

 Florida of tropical American origin and of these 

 at least a dozen have developed into distinct 

 species since they arrived here. It is probable 

 that when our flora is fully investigated quite a 

 thousand species of tropical plants will be found 

 in Lower Florida, and of these, a considerable 

 number, perhaps fifty, will prove to be endemic, 

 that is they have developed into new forms since 

 landing on our shores. 



It has required a long time for the attainment 

 of such results, for the process of establishing a 

 flora and fauna by drifting and migration must 

 necessarily be a slow one, and the development of 

 species takes much time. Ages have been re- 

 quired for all this and it is not unlikely that twenty 

 or twenty-five thousand years have elapsed since 

 the mid-Pleistocene elevation began. 



