392 
and a moderate number of minor species, 
is an area 5 times as large as the smallest 
representative area and usually contains 
1.44 to 1.5 times as many species. It is 
the smallest size to be used if a single one- 
piece sample is to be examined. The fair- 
sized stand (Af) is an area 50 times as 
large as the smallest representative area 
and contains twice as many species. 
For Sampson prairie, the curve indi- 
cates the smallest representative area to 
be 0.76 milacre, with 10.8 species; the 
computed minimum area 3.80 milacres, 
with 15.6 species, or 1.444 times as many 
species as in the smallest representative 
area; the fair-sized stand 38.0 milacres, 
with 21.6 species. 
For Phegley prairie, the curve indi- 
cates the smallest representative area to 
be 1.26 milacres, with 14.3 species; the 
computed minimum area 6.30 milacres, 
with 21.4 species, or 1.497 times the num- 
ber in the smallest representative area; the 
fair-sized stand 63.0 milacres, with 28.6 
species. 
The 9-milacre square was larger than 
the smallest representative area and mini- 
mum area for both prairies. Both prairies 
were of more than sufficient size to qual- 
ify as fair-sized stands. The number of 
species in 1 acre was estimated to be 28.0 
in Sampson and 35.2 in Phegley. 
Summary of Pastured and Unpas- 
tured Prairies.—Some of the differences 
in vegetation of the pastured and the un- 
pastured hill prairies are here summarized. 
1. The number of species in a quadrat 
was larger in the pastured than in the un- 
pastured hill prairie. 
2. Plant density, based on the number 
of plants in a quadrat, was smaller in the 
pastured than in the unpastured prairie; 
the grass bunches were smaller, less vig- 
orous, and not so tall. 
3. Grasses constituted a smaller per- 
centage of the total number of individual 
plants in the pastured prairie than in the 
unpastured. 
4. The ground space occupied by 
grasses was smaller in the pastured prairie 
than in the unpastured. 
5. Foliage area, or crown cover, was 
understandably much smaller in the pas- 
tured than in the unpastured prairie. Also, 
the ratio of crown cover to ground space 
[Lurnors NaTurRAL History Survey BULLETIN 
Vol. 26, Art. 5 
‘> 
* 
2 
r 
3 
~ 
was smaller in the pastured prairie than 
in the unpastured prairie. 
Vegetation Characters From Other 
Stands 
In the preceding section, some analytic 
characters of vegetation were described for 
two hill prairie stands, Sampson and Pheg- 
ley prairies. Analytic characters of vege- 
tation, according to some phytosociologists, 
are those traits which are studied in each 
stand. Synthetic characters of vegetation 
are those which are studied from compari- 
sons of large numbers of stands. Presence, 
a synthetic character of vegetation, and 
seasonal aspect, also synthetic in that it 
was described from observations made on 
most of the stands of I]linois hill prairies, 
are here briefly presented. 
Presence.—Presence, as used here, is 
defined as the more or less persistent oc- 
currence of a species in the stands of a 
plant community. Used for this study 
were 36 stands of hill prairies that the 
writer visited at least twice during the 
field work. From species lists of the 36 
stands, a table was devised which lists the 
species and the stands in which they oc- 
curred, table 14. Species of forests or 
thickets and those of foreign origin were 
not included in the table unless they oc- 
curred in 18 or more of the stands. 
Three species were present in 90 per 
cent or more of the stands. They were 
Andropogon scoparius, Erigeron strigosus, 
and Bouteloua curtipendula. Six species 
were present in 80 to 89 per cent of the 
stands. ‘They were Petalostemum pur- 
pureum, Euphorbia corollata, Penstemon 
pallidus, A. gerardi, Verbena stricta, and 
Kuhnia eupatorioides. These nine species 
were the “constants” of the association; 
they can be classed as “constantly pres- 
ent.” The “commonly present’ species, 
that is, those present in 60 to 79 per cent 
of the stands, were Eupatorium altissi- 
mum, Rhus glabra, Oxalis violacea, Soli- 
dago nemoralis, Panicum scribnerianum, 
Aster oblongifolius, and Ruellia humilis. 
Species in 50 to 59 per cent of the stands 
were Linum sulcatum, Lithospermum in- 
cisum, Melilotus alba, Lespedeza capt- 
tata, Pycnanthemum pilosum, Poa pra- 
tensis, Psoralea tenuiflora, Cassia fascicu- 
