200 FLORIDA GEOLOGICAL SURVEY I3TH ANNUAL REPORT 



era and even some of the species composing it are very widely dis- 

 tributed. 



Marginal and shore vegetation (fig. 20). In shallow margins 

 of lakes and along rivers where they are not subject to much fluc- 

 tuation, as near their mouths, we commonly find a type of vegeta- 

 tion intermediate between the preceding and the saw-grass marshes 

 (described a little farther on), and grading into both. It consists 

 mostly of a few coarse monocotyledons with hollow or spongy stems 

 or petioles, like maiden cane {Paiiicnm hemitomon), saw-grass, 

 wampee (Pontederia), and Sagittaria lancifolia. Then above the 

 usual water level on sandy and peaty shores of lakes \Ve find a 

 greater variety of herbs, mostly monocotyledons, often with a few 

 scattered shrubs among them. A list of characteristic plants of such 

 places was given in the 3rd Annual Report, page 267. 



Grassy dunes. On dunes where the sand is constantly moving, 

 apparently not so much on the east coast as on the west coast, there 

 is a sparse vegetation of coarse grasses and other herbs, chiefly sea- 

 oats {Uniola paniculata) and other plants belonging to families well 

 represented in tropical America. These renew their foliage every 

 year, necessitating comparatively rapid growth and presumably in- 

 dicating moderately fertile soil, though the bulk of vegetation 

 per square yard or acre is not large on account of its very open 

 structure. A little farther back from the shore, where the sand is 

 not moving perceptibly, and much of the plant food has been leached 

 down beyond the reach of roots, the vegetation is of a much slower- 

 growing type, described below under the head of shrubs. 



Salt marshes (fig. 3). These are characteristic of shallow 

 bodies of salt water protected from wave action, where the veg- 

 etation builds up a foundation of muck just about to high tide 

 level. The characteristic plants are coarse grasses and rushes, 

 with a few scattered bushes. In warmer climates the woody plants 

 become larger and more numerous, until the marshes are replaced 

 by mangrove swamps (described farther on). 



Satv-grass marshes (fig. 36). When a lake or a large embay- 

 ment of one becomes filled with peat, especially if the water is a lit- 

 tle calcareous, the vegetation is often composed almost wholly of 

 saw-grass (Cladium effusum or Mariscus Jamaiceiisis) , an ever- 

 green sedge several feet tall. The same species also forms a fringe 



