August, 1955 
more or less slumping of loess and, as a 
consequence, possessed sizable areas with- 
out plant cover. The more gentle slopes 
near the bases of the prairies had less se- 
verely eroded surfaces, and consequently 
more plant cover, than the steep spur 
fronts, but they contained more species 
characteristic of rock ledges. 
Sizes and Shapes of Study Plots.—A 
9-milacre square was staked on the upper 
Evers: Hitt Prairies oF ILLINOIS 379 
slope of a spur of each of the prairies, 
Phegley and Sampson. These plots were 
located at some distance from the crest of 
the bluff in an attempt to exclude forest 
plants and pasture weeds. Each 9-milacre 
square was then divided into nine 1-mil- 
acre quadrats (0.001 acre or +.046 square 
meters). The central milacre of the 9- 
milacre grid was selected for mapping. 
Each central milacre was divided into 
UPHILL 
Fig. 9—A 1-milacre quadrat in the unpastured Sampson hill prairie, charted October 15 
and 16, 1951, by R. A. Evers. A, Andropogon scoparius; Li, Lecidea spp.; H, Houstonia nigrs- 
cans; D, Desmodium ciliare; S, Solidago nemoralis; B, Bouteloua curtipendula; G, Gerardia 
sp.; P, Petalostemum purpureum; F, Andropogon gerardi; L, Lespedeza capitata; Av, Agave 
virginica; E, Euphorbia corollata; Op, Opuntia rafinesquii. 
