lOS ECONOMIC BOTANY OF ALABAMA. 



12. The Lime-Sink Region. 



(Figures 41, 42.) 



The region just described passes eastward into one 

 with similar geological characters but very different soil, 

 topography and vegetation, which may be called the 

 lime-sink region, as it is a direct continuation of a region 

 so named in Georgia. About 1,300 square miles of it is 

 in Alabama and still more in West Florida and South- 

 west Georgia. 



References.— Smith 6 (65, 153, 157-158), Smith 7 

 (287, 527, 538-541), Smith 8 (117-119, 667, 675-676, 

 681), Smith 9 (249, 259, plate 17A). 



Geology and soils. — The underlying formation of this 

 region is mainly the Vicksburg, as in the last, but the 

 original limestone has been very largely replaced by 

 silica, so that the rocks are mostly flinty or cherty. (It 

 is barely possible that the wetter summers and sandier 

 soil eastward may have something to do with this.) Over 

 it nearly everywhere is several feet of mottled sandy 

 clay, probably Pliocene, and on top of that in most places 

 a foot or so of whitish sand, presumably still more re- 

 cent. A tolerably pure limestone crops out in a few 

 spots, however, mostly on the banks of creeks. The 

 sandy soil was almost hopelessly sterile by ante-bellum 

 standards, but in these days of commercial fertilizers, 

 when ease of cultivation is about the best quality a soil 

 can have, it is enjoying great popularity, and being ap- 

 propriated by farmers very rapidly. 



Topography and hydrography. — The topography is 

 more nearly level than that of most of the regions previ- 

 ously described. Shallow ponds, most of which are dry 

 for a few weeks or months each year, are very common. 

 Streams are not well developed, and a good deal of the 

 drainage is subterranean (not as much so in Alabama, 

 however, as in the corresponding parts of Georgia and 

 Florida). A few caves and big springs are known, and 

 lime-sinks (an illustration of one of which is referred to 

 above) are a very characteristic though rather uncom- 

 mon feature of this region. One essential topographic 



