340 BOTANICAL GAZETTE [may 



narrow upland extending along the northern edge of Florida and 

 into Georgia, and which, on its sea-facing side, often drops abruptly 

 to the more recent coastal strip. 



The general elevation of the upland is betweeen ioo and 200 

 ft. above sea level. The surface is gently rolling with series of 

 broadly rounded or flat topped hills, in general extending east and 

 west, and alternating with open, troughlike valleys. Many of the 

 valley streams are mere swampy or boggy tracts, or they may pur- 

 sue sluggish courses which end blindly, spreading out on the surface 

 of the ground at the lowest part and soaking gradually into the soil. 

 Others end in ponds which occupy basin-like depressions, or may 

 drain into the larger lakes and sinkholes. In this hill region the 

 sinkhole origin of many large lakes as well as small ponds, and the 

 sinkhole formation along the line of some of the valleys at present, 

 suggest that the depressions of this upland division may be due in 

 large part to subterranean erosion. At any rate, no considerable 

 part of the drainage is now carried off on the surface. 



Southward from the edge of the highland there is a gradual slope 

 to the Gulf, the surface being varied only by low swells of sandy 

 soil. The St. Mark's River cuts across these sands in the south- 

 eastern corner of the county, part of its present course being due to 

 underground solution. The Wakulla River, having its origin in the 

 flatwoods, flows across the southern part of the county as a typical 

 pre-erosion stream, but is soon lost underground, to emerge at 

 length in Wakulla Spring, one of the finest large springs in the state. 

 Some of the small lakes are quite deep and constant, while the 

 majority are mere pine barren ponds, partially or entirely dried out 

 at times. Other depressions are swampy tracts known variously 

 as "bays," "galls," and "sloughs." 



Soils. — As throughout the coastal plain, the soils are chiefly 

 types of sandy series, the Soil Survey (14) stating that only about 

 one-half square mile of soil as heavy as loam or clay would be found 

 in the land surface of the county. The hills are covered by soils 

 described as derived from the Lafayette formation, while the valleys 

 and less elevated portions are covered with Columbia sands depos- 

 ited during a late period of submergence. 



