GEOLOGY AND MINERAL RESOURCES. 133 
they are available for agriculture. After drainage they may and 
frequently do constitute one of the highly productive soil types. 
The term “Hammock/’ as commonly used in contrast to pine 
lands, is applied to vegetation in which the timber growth is suf¬ 
ficiently dense to result in the accumulation of leaf mold on the 
surface. Frequently the timber growth of the hammocks is decidu¬ 
ous or largely so. This, however, is by no means essential, since the 
predominating growth may be evergreen. Again hardwoods are 
usually a conspicuous element in hammocks, and yet pines may be 
•numerous. The soil and drainage conditions in the hammocks are 
likewise variable, giving rise to a wide variation of vegetation types 
or plant groups which are more or less definitely correlated with the 
conditions of the soils, the geologic structure, topography and 
drainage conditions. 
In addition to the pine and hammock lands are the prairie lands, 
and some other types of relatively slight extent, as shown on the 
vegetation map, and described under vegetation types. 
RELATIONSHIP BETWEEN THE GEOLOGY, VEGETATION AND 
SOILS. 
That there is a definite relationship between the geology, vege¬ 
tation and the soils is apparent. The main features of the geology 
have been sketched, and it is shown that the limestones now ex¬ 
posed at the surface were formerly overlaid by clay and sandy cal¬ 
careous strata of which remnants still remain on the uplands, while 
over the whole is found the mantle of residual material which forms 
the soils. 
The stages in the development of some of the important soil 
types may be readily followed and correlated with the physiographic 
development of the region. The clay hammock lands are found 
chiefly where the Alum Bluff formation yet remains, the soil being- 
derived from the clayey and sandy strata of that formation. The 
calcareous hammock lands are found where this formation is suf¬ 
ficiently broken up to permit subterranean drainage. The rolling 
pine lands in this area represent for the most part country in which 
the disintegration of the Alum Bluff formation is complete, the soil 
having become an ochre yellow sand with a slight mixture of silt 
or loam. A further stage of disintegration results in leaching out 
largely the soluble constituents of the soil. Under these conditions 
of excessive drainage the open long-leaf pine gives place to the 
scrub oak pine lands. 
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