THE TEN THOUSAND ISLANDS 71 



no real hammock developed before the advent of 

 the mound builders. It is doubtful if any existed 

 there even while they occupied the country. The 

 people who lived there certainly created the shell 

 mounds, the only possible places on which dry- 

 land hammock could grow, and as they must have 

 lived on these mounds after they built them it is 

 more than likely the hammock growth only sprang 

 up and covered the surface after their departure. 

 It takes a long time for shells on the surface to 

 disintegrate and form a soil, on which herbaceous 

 vegetation can subsist. The gumbo limbo tree 

 was, no doubt, a precursor of the hammock, as it 

 will grow in very arid situations. After a little 

 soil was formed, seeds of the hammock trees were 

 borne in by the sea or brought by birds, and grew. 

 I counted on Chokoloskee Island over thirty 

 species of tropical trees and large shrubs, besides 

 several warm temperate forms. 



After the hammocks were established three 

 species of arboreal snails appeared and became a 

 part of their fauna. One, of these is a Liguus 

 {L. jasciatus) which is represented in the Ten 

 Thousand Islands by two quite distinct sub- 

 species; there is also the "black snail," a variant 



