GEOGRAPHY OF CENTRAL FLORIDA 193 



stitnent appear somewhat contradictory, for some of the samples 

 in the last table show more of it than one could reasonably expect. 

 Taking everything into consideration, however, it is safe to say 

 that central Florida soils generally contain less potash than those 

 of northern Florida or any equal area a few hundred miles farther 

 inland. The reason for this is probably two- fold : first, the remote- 

 ness of this area from igneous rocks which are the main original 

 source of potash, and second, the leaching effect of the copious 

 late summer rains. But this lack is partly compensated by the tem- 

 perature, for the plant food in any soil is liberated more rapidly in 

 a warm climate than in a cold one. 



The scrub and dune soils are low in potash, as in almost every- 

 thing else. 



The lime, like the potash, is as a rule most abundant in the rich- 

 est soils, and vice versa, but there are some important exceptions. 

 For example, the beach and dune sands are well supplied with cal- 

 cium carbonate in the form of shell fragments, but are practically 

 worthless for agricultural purposes, perhaps chiefly on account of 

 the scarcity of very fine particles for plant roots to draw nourish- 

 ment from (no mechanical analyses seem to be available, "unfort- 

 unately), or of soil animals and bacteria. And the vegetation of 

 the calcareous hammocks near Ocala (sample T), with over y% 

 of lime in the soil, does not seem as luxuriant as that near Mc- 

 intosh (sample U), where there is less than 2%. However, prob- 

 ably the latter figure is more than sufficient, and any excess over 

 that therefore superfluous. The least lime is in the St. John's 

 River prairie (Y), which seems rather strange, for ditches near 

 where the sample was taken show shell marl within two or three 

 feet of the surface. 



Although lime (or more strictly speaking any calcium com- 

 pound) is not an important plant food, it is thought to improve the 

 condition of the soil in various ways, and as it dissolves readily it 

 liberates less soluble plant foods that may be combined or mixed 

 with it. 



The phosphorus is almost incredibly high in samples R, T, U 

 and X, soils with more than half of one per cent of P^O^ being 

 very exceptional.* The high percentage in X, which was taken 



*See Hilgard, Tenth Census 578; 1884; Soils 355. 1906, 



