1916] 
PALMER—PLANTS OF JASPER COUNTY, MISSOURI 351 
The geological formations represented аге the Mississip- 
pian series, or Subcarboniferous, and the Pennsylvanian se- 
ries, or Coal Measures. The Mississippian occupies much 
the greater portion of the area. The rocks of this series con- 
sist mainly of heavily bedded, semi-crystalline limestones 
interbedded with lenses of chert, which in places predomi- 
nates over the limestone. As the silicious rocks are much 
less soluble than the ealeareous beds, large deposits of angu- 
lar chert fragments, more or less imbedded in red iron- 
stained clay, occur locally where the higher beds of lime- 
stone have been removed by erosion. The horizontal strata 
of limestone form bold escarpments and bluffs along the 
river valleys and sometimes outerop through the mantle of 
residuum on slopes and high hills. 
The Pennsylvanian formations, consisting of shales and 
sandstones of the Cherokee group, occupy the northwestern 
corner of the county, covering portions of Jasper and Twin 
Groves and the greater part of Preston and Duval Town- 
ships. Small isolated areas to the southward are too lim- 
ited in extent to have much influence upon the flora. The 
rocks of this series, being soft and friable, give rise to a dis- 
tinct topography with gentle slopes and low hills, through 
which flow sluggish intermittent streams. The influence upon 
the flora of these differences in soil and physical features is 
quite marked. 
An interesting geological feature is the occurrence of 
water-worn river gravels covering some of the higher eleva- 
tions through the south-central portion of the county. These 
deposits, which have been referred to the Lafayette Gravel of 
Tertiary age, are of very limited extent, but will be men- 
tioned in connection with the flora. 
In so limited an area climatic influences are, of course, 
essentially uniform, and the variations in altitude are not 
sufficiently great to affect plant life except indirectly. Over 
the bulk of the area, underlaid by Mississippian rocks, the 
factors which determine plant associations and restrict the 
range of certain species are moisture, shade, and the local 
