PLANT ASSOCIATIONS OF WESTERN PENNSYLVANIA 151 



the beech. The chestnut and maple have the abiUty to adapt 

 themselves to the rich mesophytic forest, or to the more exposed 

 slopes of the uplands. 



The shrubby and herbaceous flora necessarily varies in com- 

 position as the tree membership varies; but is always conspicu- 

 ous for its large number of species. The following forms include 

 the more important members: Hamamelis virginiana, Ribes 

 gracile, Ribes oxycanthoides, Ribes floridum, Rubus idceus, Rubus 

 allegheniensis, Smilax hispida, Smilax herbacea, Lycopodium 

 obscurum, , Lycopodium lucidulum, Lycopodium complanatum, 

 Lycopodium clavatum, Lonicera americana, Mitchella repens^ 

 Psedera quinquefolia, Pteris aquilina, Botrychium virginianum, 

 Fragaria virginiana, Osmorhiza longistylis, Aralia nudicaulis, 

 Podophyllum, Anemonella thalictroides, Oakesia sessilifolia, Aris- 

 cema triphyllum, Geranium maculatum, Cypripedium acaule, 

 Boehmeria cylindrica, Uvularia grandiflora, Uvularia perfoliata, 

 Onoclea sensibilis, Aspidium spinulosum, Aspidium noveboracense^ 

 Phegopteris hexagonoptera, Polygonatum biflorum, Polystichum. 

 acrostichoides, Smilacina racemosa, Osmunda Claytoniana, Os- 

 munda cinnamomea, Medeola virginiana, Trillium graridiflorum^ 

 Trillium sessile, Viola pubescens, Viola pallens, Carex pennsyl- 

 vanica, Maianthemum canadense, Monotropa uniflora, Epifagus 

 virginiana, Aster umbellatus. Aster cordif alius, Solidago coesia, 

 Prenanthes alba, Prenanthes altissima, Habenaria Hookeri, Epi- 

 pactus repens, Sambucus racemosa, Asplenium Filix-fcemina, 

 Asplenium platyneuron, Trientalis americana, Gaultheria pro- 

 cumbens, Polytrichum commune, Corallorrhiza maculata, Galium 

 circoBzans, Carex platyphylla, Carex pennsylvanica, Euonymus 

 obovatus, Vitis labrusca, Rhus toxicodendron, Tiarella cordifolia, 

 Mitella diphylla, Circcea lutetiana, Streptopus amplexifolius, etc. 



Upon Unglaciated Clays 



To the east of the glacial drift the topography is strikingly 

 irregular, being cut up into a great series of hills and valleys by 

 the erosive activity of numerous small streams. Clay soils 

 predominate throughout most of this region. The structural 



THE PLANT WORLD, VOL. 20, NO. 5 



