120 



NINTH REPORT. 



pact, even this side-wash is reduced, largely on account of the delayed down- 

 ward flow of water, and the consequently greater absorption of it by the soil. 

 Absence of vertical erosion and of meandering due to ravine rills and streams 

 has increased the favorable conditions necessary for plant life, but the lim- 

 ited drainage is not advantageous to the formation of a mesophytic flora, 

 either of vernal or estival forms. About midway the outcropping of an im- 

 pervious and compact clay, which underlies the whole region, and appears 

 elsewhere at the surface, is important, because of the relations existing be- 

 tween the upper and lower soil types and the associated plant societies. 

 There is a slow but constant flow and percolation of water, and the distri- 

 bution of plants as influenced by conditions of soil nioisture gives rise to im- 

 portant differences. A profile was made, shown in Fig. — -, and is added 

 here through the courtesy of Dr. Burns. 



Fig. 1. 



The moisture in the soil is retained for considerable depth. Tracts of low, 

 wet ground occur at the mouth and such moisture-preferring plants as Im- 

 patiens fulva, Gentiana flavida, Solidago flexicaulis, Equisetum hyemale, 

 Eupatorium ageratoides, Pedicularis lanceolata, Ivobelia syphilitica, Aster 

 lowrieanus are frequent. Mosses, liverworts and fungi are well represented. 

 The intermediate zone is a dense profusion of ferns, such as Adiantum pe- 

 datum, Asplenium felix-fcemina, Onoclea sensibilis, O. struthiopteris, Os- 

 munda regalis, 0. claytoniana, 0. cinnamomea, Dryopteris acrostichoides 

 with Pteris aquilina and Phegopteris hexagonoptera higher up. The ar- 

 rangement varies from place to place. Shrubs such as Corylus americana, 

 may be thickly clustered ; in other parts a loose growth of oak and hickory 

 saplings, or of Cornus candidissima, Avith climbers such as Celastris scandens, 

 Dioscorea villosa and Smilax herbacea, covers the ground. In passing up- 

 ward the herbaceous vegetation includes Thalictrum dioicum, Vagnera 

 racemosa, Eupatorium purpureum, Smilax hispida, Meibomia grandiflora, 

 and nearer the divide are found Meibomia rigida, M. Michauxii, Lespedeza 

 violacea, Vaccinium vacillans, Rosa humilis, Helianthus divaricatus, Salix 

 humilis, Corylus americana, Rhus hirta, and several perennial grasses and 

 composites, already indicated in the first ravine described. 



