380 
64+ small squares of 1/64 milacre (ap- 
proximately 6.25 square decimeters) to 
facilitate mapping. These small units 
were combined in working over the data 
to give 1/16-, 1/4-, and 1-milacre plots. 
The central milacre quadrat in the Pheg- 
ley prairie was mapped, fig. 8, and the 
shoots in this milacre were counted on 
October 9 and 10, 1951, by the writer 
=< | 
33! 
SAMPSON (UNGRAZED) 
Intinoris NaruraAt History Survey BULLETIN 
<— DOWN SLOPE 
Vol. 26, Art. 5 
each with an area of 5 milacres and five 
each of 10 milacres. Species lists were 
then compiled for the staked areas of each 
prairie by units of 1/64, 1/16, 1/4, 1, 3, 
5, 9, 10, 25, 50, and 75 (303.5 square 
meters) milacres. 
From data obtained from the staked 
areas, it was possible to determine the 
number of plant species and number of 
PHEGLEY (GRAZED) 
Fig. 10—Arrangement of plots and strips in two hill prairies. Each shaded square repre- 
sents the mapped central milacre of a 9-milacre grid. 
with the assistance of Dr. A. G. Vestal; 
the central milacre in Sampson prairie was 
mapped, fig. 9, and the shoots were 
counted on October 15 and 16, 1951, by 
the writer. In addition, a list of plant 
species was made for each 1/4 milacre in 
the other 8 milacres of each of the 9-mil- 
acre grids. 
In order to find the increase in number 
of species with an increase in area, the 
writer staked a 25-milacre square and a 
50-milacre rectangle in each of the two 
prairies, fig. 10. In Phegley, the 25-mil- 
acre square was downslope from the north 
half of the 50-milacre plot, the half that 
included the 9-milacre square. In Samp- 
son, because of the proximity of woodland, 
the arrangement could not be made iden- 
tical with the arrangement of plots in 
Phegley: the 9-milacre square was inside 
the 25-milacre square; the south half of 
the 50-milacre rectangle was downslope 
from the 25-milacre square. The staked 
25- and 50-milacre plots were divided into 
strips 6.6 feet wide, making five strips 
shoots in plots of various sizes; for each 
species, the frequency of occurrence in 
plots; for each of the several grass spe- 
cies, the area covered or ground space of 
plants; and, for all species collectively, the 
estimated number of plants per unit of 
area and the available space per plant. 
Comparisons between pastured and un- 
pastured hill prairie were made. From 
the data it was possible to construct a 
species-area curve and from the curve to 
find the sizes of certain reference areas, 
as will be explained later in this section. 
Method of Counting Plant Units.— 
For plants other than grasses, each shoot 
that appeared above the ground surface 
and was without obvious connection to 
another shoot was counted as one unit, or 
individual. For example, each single 
rosette of Solidago nemoralis was counted 
as one individual; each shoot of Howsto- 
nia nigricans, Petalostemum purpureum, 
and Desmodium ciliare was counted as 
one individual unless connections with 
other shoots could be traced. 
