554 HARPER: PINE-BARREN VEGETATION OF MIssISSIPPI 
other pine-barren regions represent distinct formations of late 
Tertiary or Quaternary age (Columbia and Lafayette), or are 
merely products of weathering from the underlying marine 
Tertiary formations.* 
Deep beds of sand, such as are common on the left sides of 
creeks and rivers in the corresponding parts of Georgia, are rare 
in Mississippi, and the Mississippi pine-barren soils seem to 
average a little richer than those farther east. But in comparison 
with soils farther inland these are poor in available mineral 
plant food, especially near the coast, where the diminished seasonal 
fluctuation of the ground-water seems to limit the supply of 
available potash, etc., in a manner not yet fully understood, but 
perhaps simply by preventing aeration. The richest soils in this 
region are along streams which pass through calcareous regions 
farther inland, and west of the Pearl River where the influence of 
the loess is felt. 
The following partial ce ias extracted from Dr. Hilgard’s 
report on Mississippi in the 5th volume of the Tenth Census will 
serve as a basis for comparing these soils with those of northern 
Mississippi and other nearby or similar regions. They are from 
three localities, a pine ridge in Simpson County, the hammock 
or second bottom of the Pearl River in Marion County, and the 
“pine meadows” of Jackson County. In the first two cases both 
soil and subsoil were analyzed. The percentages of only lime 
(CaO), potash (K,0), “phosphoric acid” (P.O;), and magnesia 
(MgO) are given here. 
All of these, especially the last, are considerably below the 
7 Pea mey = the pesiend hypothesis clade at the process of weathering tends 
to wach 
his were universally 
. true then ‘the hehe soils would be the sandiest; but in the interior hardwood region 
we g-, in Middle Tennessee, Kentucky, etc.), where the soils are residual from Paleo- 
zoic ss and have been exposed to weathering processes many times longer than 
the region under consideration, clay predominates on the surface, and sand is chiefly 
confined to the beds of streams. Even on the Cumberland Plateau, where the rocks 
are mostly sandstone, the soils are decidedly loamy. To explain this difference 
between the soils of Tennessee and southern Mississippi it will probably be necessary 
to take into consideration the ep distribution of rainfall. In Middle Tennessee 
and a great deal of neighboring territory the summers are pretty dry, while in the 
region under consideration, as in most other parts of the coastal plain, summer is the 
rainy season; which must make a considerable difference in the processes of weather- 
ing. 
