524 Part IV. Chapter 3. 
becomes raised more and more above the lake and grasses follow the sedges 
forming a prairie. Sometimes with the prairie grasses are a number of coarse 
herbs Silphium laciniatum, S. terebinthinaceum, S. integrifolinm, Solidago 
rigida, Allium cernuum ')). 
ora of the wet prairies in Illinois is mixed with the species of the neighboring 
banks, swamps and bottom-woods and differs according to the soil. Tall grasses such as Calama- 
grostis canadensis, Leersia (Homalocenchrus) lenticularis, ne TEE a Ahomnd mixed with 
sedges as Scirpus, a Carex rn oidea, C. erus-corvi, C. stipata, C. conjuncta, C. scoparia, 
straminea, C. hystric The most conspicuous Verbacsei: Be # the ne are: Meny- 
anthes trifoliata, ee, Allium canadensis; of the summer, Phlox glaberrima, 
Asclepias Sullivantii, ne ee Steironema lanceolata, Ipomoea lacunosa, Habenaria 
leucophaea; of the tonia on Prenanthes (Nabalus) racemosa, Solidago neg- 
lecta, S. Ridellü, S. re ls giganteus, Gentiana Andrewsii and Polygonum ramosissimum. 
e grassy slopes in the St. Croix be where the soil is brownish, or blackish, 
are covered by Bouteloua curtipendula, Andropogon scoparius, Koeleria cristata, and such early 
flowing herbs as Viola pedatifida, V. pedata, Arabis lyrata, Phlox pilosa, Silene anitirrhina, while 
later in the season appear Ceanothus americanus, Delphinium azureum (= D. carolinianum), Soli- 
dago rigida, S. eh and Rosa blanda. 
The Bor of the Wisconsin drift consists of the characteristie prairie en including 
wg of Liatris and Andropogon, auge 2 Phlox pilosa, Panicum Scribnerianum, P. 
‚ Vieia americana, Geranium mac ,‚ Echin urpurea, Lithospermum canescens, L. 
ER Viola palmata, V, pedata, ehe en Astragalus caryocarpus (= A. crassi- 
carpus), Stipa spartea, etc. Polytaenia Nuttallii, Ceanothus ovatus, Baptisia leucophaea, Rudbeckia 
hirta, Oenothera serrulata. The plants of the lower and Sig areas are: Anemone pennsylvanica, 
halictram purpurascens, Juncus tenuis, Panicum Seribner P. virgatum, Liatris scariosa, L. 
pyenostachya, Vicia americana, Baptisia leucantha, Lilium Bde kieiin, L. canadensis, Lathyrus 
venosus and Cicuta maculata2). 
Sand Prairie Formation. The plant associations of the sand prairies 
are three: the bunch-grass, the blow-sand and the blow-out associations. 
The Bunch Grass Association (see Fig. 27) is characterized by Eragrostis 
trichodes, Stipa spartea, Panicum cognatum in dense flat bunches scarcely a 
foot high, Triodia cuprea (= Tricuspis seslerioides), Calamagrostis (Calamo- 
vilfa) longifolia, Eragrostis pectinacea, Bouteloua hirsuta, Panicum virgatum, 
aspalum setaceum and Sporobolus ceryptandrus also produce more or less 
well-developed bunches. Here also occur Carer gravida, Cyperus ‚Schrwei- 
nitzii and C. filiculmis. 
The Blow-Sand Association occurs where the wind causes a shifting 
of the sand, which if excessive remains without vegetation. The mat-like 
Opuntia Iuweifu the dense clumps of Amorpha canescens or Chrysopsis cam- 
forum may be effectual in anchoring such drifting sand. ‘The most typical 
plants of this association are Ambdrosia psilostachya, Cassia chamaecrista, 
Cenchrus tribuloides, Cycloloma atriplicifolium (= C. platyphyllum), Cristatella 
Famesii and Aristida tuberculosa. The vegetation of the front of an advan- 
cing dune is different from that of the blow-sand association. 
I) See Cowres, H. C.: Physiographie Ecology of Chicago and Vieinity. Botanical Gazette 
XXXI: 155 Feb. and March 1901 
2) PAMMEL, L, H.: Coiipaaaläve Study of Vegetation, ete. loc, eit. 
