VESTAL: A BLACK-SOIL PRAIRIE STATION 359 
1 Iris versicolor, ch l,i Valeriana edulis 
f Thalictrum dasycarpum, ch 1, i Lobelia syphilitica 
i Hypericum sp. 1, f Eupatorium perfoliatum, m 
f, Id Eryngium yuccifolium, ch ld Liatris spicata, ch 
f Cicuta maculata, ch | Sohdago Riddellii, m 
i Thaspium aureum 1 Solidago ohioensts 
f Oxypolis rigidior, ch i Aster paniculatus? 
l,i Gentiana Andrewsii? lf Parthenium integrifolium, m 
1 Apocynum cannabinum i Senecio Balsamitae 
What may be called the Eryngium consocies of swamp prairie is 
characterized by dominance of this peculiar umbellifer, and cor- 
responds fairly well with the low prairie of Cowles.* This growth 
shades into the Silphium terebinthinaceum consocies of the meso- 
phytic prairie-grass association, Silphium and Eryngium frequently 
being seen together in about equal abundance. This is then the 
transitional growth between hydrophytic and mesophytic prairie. 
he plants conspicuous in this intermediate prairie are marked 
“h, ch” in the list of mesophytic prairie-grass species. 
The marsh associations.—Areas of marsh vegetation are usually 
scattered and not large. There are now few areas of open water, 
since many of the ponds and swamps west of Chicago have been 
artificially drained. Marsh growths are commonly dominated by 
a single or by very few plant species. Prominent among these 
are Spartina Michauxiana, Calamagrostis canadensis, Phragmites 
communis, Glyceria nervata, Scirpus lineatus, and Typha latifolia. 
Willows (Salix longifolia) and cottonwoods (Populus deltoides) are 
able to establish themselves on the margins of some of these 
swamps, particularly in mud flats left bysummer shrinking of ponds. 
A small pond near the southwest corner of the area mapped, and 
the slough directly east of this pond, are thus margined with good- 
sized trees. 
The zone marked “‘ A grostis’’-in the map is probably disturbed 
swamp prairie. It is now dominated by the single grass species 
Agrostis alba (red-top), and there are also a few swamp prairie 
plants, as Cicuta maculata. Lower ground is occupied by a vir- 
* Cowles, H. C. The physiographic ecology of Chicago and vicinity. Bot. 
Gaz. 31: 73-108, 145-182. 1001. (Low prairie, p. 156. 
