354 VESTAL: A BLACK-SOIL PRAIRIE STATION 
prairie-grass, and (3) hydrophytic or swamp prairie, or fen. It 
should be noted that these intergrade, passing into one another 
gradually, instead of alternating sharply, and that many species 
tolerate a wide range of soil moisture and of other environmental 
conditions, so that some species are found abundantly in more than 
one association. Some species, too, reach greatest abundance in 
transitional growths intermediate between two associations. 
The xerophytic prairie-grass association——This growth is not 
very extensively developed in upper Wisconsin glaciation of 
northeastern Illinois. Its best representative is the Silphium 
laciniatum consocies. The dominant species, often called the 
compass-plant, is very conspicuous. This type of prairie is rather 
locally seen in eastern Du Page County, and is hardly at all 
represented at the county line. Following is a list of species 
typical not only of the Silphium laciniatum prairie, but of the 
xerophytic prairie-grass association in general, as represented in 
eastern Du Page County. 
*SPECIES TYPICAL OF XEROPHYTIC PRAIRIE-GRASS 
dor ld Andropogon scoparius, ch i Verbena stricta 
| Andropogon furcatus, m | Physalis virginiana 
| Sorghastrum nutans, m | Liatris scariosa 
| Panicum virgatum lf Solidago nemoralis 
1 Stipa spartea f Solidago canadensis 
1 Sporobolus heterolepis, m lf Solidago serotina 
{ Koeleria cristata lf Solidago rigida, ch 
| Comandra umbellata , i Aster sericeus 
f Rosa humilis f Aster multiflorus, ch 
l Cassia Chamaecrista a3 Erigeron ramosus 
ag totation as used in the above table « of species, and in other tables of this 
article, is as follows: symbols to the left of the species name have to do with frequence 
or abundance of the species in the station or in the association; d = dominant, 
a = frequent, i = infrequent, | = local, of scattered distribution, or 
prefixed = locally; symbols to the right of the name have to do with the degree to 
which the species is characteristic of this or of other associations and habitats; 
more typical of, or a relic from, co comparatively SAY Soap communities, or in very 
local depressions within mesophytic prairie gro 
