THE ORIGIN OF THE HAMMOCKS 191 



southern edge of the mainland the vegetation of 

 these hammocks is mostly tropical; over the 

 balance of our area it is a mixture of tropical and 

 warm temperate growths, or almost wholly tem- 

 perate and warm temperate. The vegetation of 

 the swamps and lowlands is less tropical than that 

 of the corresponding uplands, probably because 

 the soil in the two former is colder. 



The majority of the fruits of our hammock trees 

 and shrubs are either berries or drupes (plum-like). 

 Generally these are attractive in color and are 

 greatly relished by birds. In fact they constitute 

 for many of them their chief food, and a hammock, 

 in any region, always attracts great numbers of 

 birds. In eating the fruit they swallow the seeds 

 as well, which are passed out undigested and with 

 their vitahty unimpaired. Thus they are scat- 

 tered broadcast in every direction — in the pine 

 woods, the swamps — everyivhere. So, then, the 

 birds become horticulturists and are responsible 

 for the dispersal of many of our plants. Nature 

 has drawn up a contract between these little 

 farmers and the trees. The latter must have 

 their seeds distributed and planted elsewhere to 

 maintain and spread their species and to form new 



