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HARSHBERGER: PHYTO-GEOGRAPHIC SKETCH 145 
surrounding country. The dominant trees on the serpentine bar- 
rens are Quercus alba L., Q. stellata Wang., Quercus Marylandica 
Muench, Acer rubrum L., Lirivdendron Tulipifera L., Nyssa syl- 
vatica Marsh., Juniperus Virginiana L., Castanea dentata (Marsh.) 
Borkh., Fagus Americana Sweet, Quercus rubra L. and Prunus 
serotina Ehrh., while associated with these trees are Sassafras 
Sassafras (L.) Karst. Rhus glabra L., Kalmia latifolia L., Salix 
tristis Ait., Cornus florida L., Viburnum dentatum L., Polycodium 
stamineum (L.) Greene, Gaylussacia resinosa (Ait.) Torr. & Gray, 
Viburnum acerifolium L. and Benzoin Benszoin (L.) Coult. The 
lianes are Vitis aestivalis Michx., Parthenocissus quinquefolia ( L.) 
Planch., Rhus radicans L., Smilax rotundifolia L. and S. glauca 
Walt. 
The herbaceous plants of the forest floor are found in pure 
association, or they occur sparingly distributed along with other 
herbs that form together a mixed vegetation. The habitats of the 
different herbaceous associations are controlled by photic and 
edaphic conditions. Thus in the deep shade of the dominant 
trees, the botanist finds the following plants forming pure associa- 
tions and each association may be distinguished by the generic 
Name of the plant : 
April. — Asarum Canadense ., Bicuculla cucullaria (L.) 
Millsp. (Dicentra cucullaria DC.), Erythronium Americanum Ker, 
Claytonia Virginica L., Pedicularis Canadensis L., Epigaca repens 
Lam., Thalictrum dioicum L. 
May. — Cubelium concolor (Forst.) Raf. (Solea concolor Ging.), 
Podophyllum peltatum 1., Triosteum perfoliatum L., Tradescantia 
Vir, giniana L,., Mertensia Virginica (L.) DC., Caulophyllum thalic- 
trowdes (L.) Michx., Hydrophyllum Virginicum L. ~ 
July. — Gaultheria procumbens L. 
The following ferns are also found in pure association in the 
forest : Adiantum pedatum 1., Dryopteris spinulosa (Retz) Kuntze, 
(Aspidium spinulosum Swartz), Dryopteris marginalis (L.) i AY 
(Aspidium marginale Swartz), Dryopterts acrostichoides (Michx.) 
Kuntze (Aspidium acrostichoides Sw.) and Phegopterts Phegopterts 
(L.) Underw. (P. polypodioides Fée). | 
Along the woodland streams, growing in the damp loamy soil 
of such situations and controlled by the amount of soil-moisture 
