‘No. 17] FLOWERING PLANTS AND FERNS 47 
cent region, together with a few others most commonly found 
in the lowlands, are given here: 
Polygcnum Virginianum Hymenoeallis lacera 
Commelina hirtella Lythrum alatum (openings) 
Penthorum sedoides Ammannia coccinea 
Lippia lanceolata Spermacoce glabra 
Saururus cernuus Conobea multifida 
Asclepias perennis Spilanthes repens 
Jackson Prairie Region.—This region of small prairies ex- 
tends in a belt varying from 10 to 30 miles miles wide, in a 
directicn slightly northwest and southeast across the state 
(boundaries may be seen on the sketch map). Its greatest 
breadth is in the extreme western part from the longitude’ of 
Jackson to the Bluff Hills; eastward it narrows to the Alaba- 
ma line. The region is one of rolling topography. In parts, 
as in the southern half of Madiscn County and the northern 
part of Hinds, the surface is gently rolling; in other parts 
where the soil is sandy, the topography is more broken. In the 
broad western part of the area the surface soil is Brown Loam 
of loess origin modified somewhat by the underlying cacareous 
Jackson clays; the sandy, hilly parts have a soil derived from 
the overlapping cf the Jackson clays by red and yellowish 
sands of the Pliocene beds. 
The typical prairie soils are rather heavy dark gray, or, 
in much of the area, lighter gray clays produced by the weather- 
ing of the calcareous clays and marls of the Jackson formation. 
This character of soil is not found in continuity over wide 
spaces, but is generally patchy, the patches being surrounded 
by one of the other types. 
As would be expected, the flora of the region presents three 
rather well-marked phases. The typical soil, that of the true 
prairie type, supports a characteristic prairie flora; the west- 
tern loam part supports the flora of the Brown Loam region, 
modified by invasions from the prairie flora, and the sandy 
loam parts toward the southeast support the extensions of the 
flora of the southern long-leaf pine belt, modified by additions 
from the prairie flora. 
