Transition Prairie-Forest District. 525 
The Blow-out Association exists where the wind has scooped out 
hollows in the sand and an entirely new set of plants occupies the ground. 
Fimbristylis capillaris first appears and forms a carpet over the flat bottom 
of the blow-out, ultimately forming a thin layer of black humus over the 
surface. Assöäisted with it are large clumps of Panicum virgatum, and Andro- 
pogon furcatus. With these grasses are often associated Viris vulpina, Meni- 
spermum canadense, Populus momilifera, Negundo aceroides. The two vines 
scramble over the ground and the trees grow rapidly. Lichens of the genus 
Cladonia appear and are succeeded by Helianthus occidentalis, H. rigidus 
(= H. scaberrimus), Liatris scariosa, and Cacalia atriplicifolia‘). 
Sand Prairie Formation. These associations occur near the mouths of the 
principal rivers that are tributary to the northern Mississippi River in Wis- 
consin and elsewhere®),. The only arboreous vegetation growing on these 
prairies are Ouercus macrocarpa, O. tinctoria and occasionally Fraxinus viridis 
and Betula lenta. These trees, however, occur only in close proximity to the 
Mississippi bottoms. 
Prairie Swamp Formation. The marshes of the transition prairie-forest 
country are the sources of perennial springs, which if of sufficient size form 
small streams that are lined by Salir discolor and S. Richardsonii. Confined 
to the marsh edges are S. candida, S. lucida, while Alnus incana and Cornus 
stolonifera are characteristic shrubs. 
The commoner plants of these marshes are Saxifraga pennsylvanica, Thalictrum purpurascens, 
Viola blanda, Iris ragen a nervata, Parnassia une Lilium canadense, Pedicularis 
Isareolain, Lycopus s americanus), Menth er Stachys palustris, Gentiana 
ita, G. Andrewsi, rg coccinea, Heracleum lanat aleriana edulis, Onleui Nere 
muticus, Archangelica (Angelica) atropurpurea, Er ara tum, Cardamine rhom 
Bromus Kalmii, while Cypripedium candidum, Caltha palustris, Viola blanda, V. — var. 
Muhlenbergii (ui labradorica) and Bleu en are local plants found in proximity to 
the springs. 
The species of the larger open swamps in the Sa country of Illinois are: Epilobium 
palustre, E. coloratum, Proserpinaca palustris, Cicuta maculata, Sium eicutaefolium, Aster phoeni- 
ceus, A. novi-Belgii, A. junceus, A. salieifolius, A. rare Acorus calamus, Typha latifolia, 
Triglochin palustris, T. märitima, Dulichium spathaceum (= D. arundinaceum), Kleocharke palustris, 
Eriophorum re Rhynchospora alba, Carex STE C. teretiuscula, C. filiformis, C. co- 
mosa, C. riparia, C. monile, Muhlenbergia glomerata (= M. racemosa), Phragmites, Phalaris aru- 
dinacea, Nephrodiun (Aspidium) thelypteris, — regalis. 
The alluvial marshes along the sloughs of the gg = Black Rivers are common 
and siallir situations along the Wisconsin River s as Ranunculus multihidus 
(= R. delphinifolius), Sarracenia purpurea, Viola a Er lass longifolia, Hypericum 
BR Potentilla palustris, Saxifraga pennsylvanica, Parnassia caroliniana, Lythrum alatum, 
Epilobium lineare, ass bulbifera Ser: trifidu gr perfoliatum, Boltonia asteroides, 
Aster novae-Angliae, A. Trades Coreopsis (Bidens) trichosperma, Campanula aparinoldes, 
Gentiana Andrewsi, een FRE: Chelone glabra, ee anagallis, Gerardia purpurea, 
ı) C. A. Hart and H. A. GLEASoM (loco citato 
2) Pammeı, L. H.: Forest vegetation of the SR = Mlaiaisot Garden and Forest IV: u 
472, 531. 
