I 



19 1 7] GANO— ECOLOGY OF FLORIDA 365 



In such sinks the water rises and falls with the amount of precipi- 

 tation and surface drainage. Other sinks are dry, having one or 

 more openings in connection with the underground drainage system. 

 The cliffs and ledges of limestone, if exposed, soon wear off, soil 

 collects, and gradually the sides become overgrown. The soil 



om 



m 



moisture favoring the growth of su< 

 d mosses may be found on the damp 



Liver- 



sink and often in the crevices of the sides. Adiantum capillus- 

 veneris L. belongs to such situations, as also Poly podium polypo- 

 dioides Hitchc, Asplenium platyneuron Oakes, and Polystichum 



acrostic hoides Schott. 



Opelismen 



setarius L. are grasses in the shady ravine-like situations, as pioneers 

 on the sides. 



If the sink contains water, pond plants will enter and cypresses 

 or gums may grow. If the base is covered or finally filled with 

 soil, water oaks, live oaks, sweet gums, dogwood, and holly are 

 common sinkhole plants. White oaks, red maples, black gums, and 

 sweet gums are other trees occurring about the sinkhole margins. 



Springs. — Many springs are the results of channels in the lime- 

 stones, occurring where the streams emerge from underground. 

 In the clear, cool, calcareous water of such springs there is not 

 much plant growth, although around the margins are grasses, 

 sedges, sagittarias, and reeds. 



Lakes and ponds. — The relation of the large lakes to sink- 

 hole formation has been mentioned, sinks or openings occurring in 

 their basins through which the more or less complete drainage of 

 the waters of the lake may take place suddenly or gradually. 

 When these sinks become closed by obstructions or stoppage, the 

 water will again fill the basins (12). By the drainage of such lakes, 



forest stage. 



become p: 

 gradually 



Streams. — Underground channels sometimes become surface 



I in of the roof of the cavern. Frequently 



streams by the cavin 

 a section may be left 



Such is the case 



