244 IN LOWER FLORIDA WILDS 



half floating on the water. It sends up from its 

 stems roots which resemble ordinary ones, but 

 their office is strictly to aerate the plant for in 

 reality they are simply oxygen pumps. The 

 beautiful Crinum americanum with its large, 

 starry, pure white flowers is often common along 

 the banks and one or more of the elegant spider 

 lilies (Hymenocallis) are seen peeping out of the 

 saw grass. Farther up the estuary where the 

 ground rises a little Myrica or wax myrtle, Annona 

 or pond apple, coco plums (Chrysobalanus), and 

 the swamp magnolia begin to appear. 



At the end of the brackish water where the 

 rapids commence, a small mollusk is sometimes 

 found in great numbers on the rocks. This is one 

 of theNeritinas (N. reclivata) . Its nearly globular 

 shell is dark green with narrow, longitudinal 

 black stripes, and the accomplished animal can 

 live in fresh or brackish water or even in the air. 

 It is probably in process of becoming an air- 

 breather altogether. Two members of the same 

 genus live in the open sea along our coasts; this 

 has gone landward to the intersection of fresh and 

 brackish water, while several species in other 

 regions live in water that is wholly fresh, and at 



