545 
from Odin to Olney is covered by Andropogon furcatus, and much of 
it is original prairie sod. 
Still another type of reversion to the Andropogon waits prairie 
may be seen on eroding banks and slopes along these rights-of-way. 
Many instances were noted where Andropogon scoparius dominated 
the slopes of valleys while the upland and base of the slopes were domi- 
nated by Andropogon furcatus. The successions of these associations 
accompanying base-leveling in such cases is obvious. Sorghastrum 
nutans and Sporobolus heterolepis were also found on these slopes but 
generally as secondary species. Where erosion is rapid coarse herbs are 
abundant, but where erosion is slowed down by decreased gradients 
and consequent greater stability of soil they become scattered secon- 
dary members of the grass associations. In cases where the natural 
grasses have been entirely eradicated these coarse herbs prevail perhaps 
indefinitely. 
In addition to railway rights-of-way in the Illinoisan glaciation old 
fence-rows harboring relic patches of prairie plants are abundant. When 
land adjoining these fence-rows is sowed to meadow grasses the culti- 
vated grasses are gradually invaded and crowded out by Andropogon 
furcatus. One instance was observed where this native grass occupied an 
area of timothy meadow to a distance of 40 feet, and areas 10-15 feet in 
width are common. 
With regard to limitations in basing conclusions upon statements 
made by the early settlers the principle that safety lies in numbers was 
adhered to, and in practically all cases specimens of the plants in ques- 
tion were at hand. No less than 30 individuals were questioned with 
regard to the original prairies of the Southern Illinoisan glaciation. 
Many of these had spent from 20 to 30 years on the virgin prairies and 
on account of economic, medicinal, or esthetic reasons were familiar with 
many species of prairie plants. 
The data obtained from the early settlers and a careful study of 
the prairie relics seem sufficient to reconstruct rather accurately the 
original prairies of the Southern Illinoisan glaciation. The !ow prairie 
was dominated mainly by Spartina Michauxiana, Calamagrostis cana- 
densis, and Panicum virgaium, while the more extensive prairie was 
dominated by Andropogon furcatus. Coarse herbs grew only as scattered 
individuals among the grasses. On the exposed clay Andropogon scopa- 
rius was abundant, and associated with it were many coarse herbs. A 
mixed association consisting of the two Andropogons, Sorghastrum nu- 
tans, and Sporobolus heterolepis may have occurred in transition zones 
on some of these clay areas. 
Turning now to the Wisconsin glaciation the same sources of in- 
formation exist, but they were less fruitful. From the data available 
it is certain than Andropogon furcatus was the dominant grass of the 
upland prairies. The points in question concern the probable role played 
by coarse herbs and by more xerophytic grasses, particularly Andropogon 
