PAPERS ON BIOLOGY AND AGRICULTURE 175 



a score of deer have been introduced, but their effects are 

 negligible. The area, too, is one having sufficient topographic 

 diversity to be representative. In the climax expression 

 Quercus alba is still probably the dominant species. The 

 other representative species are Acer saccharum, A. nigrum, 

 Hicoria minima, Prunus serotina. Juglans spp., Tilia ameri- 

 cana, Fraxinus spp., Ulmus spp., Quercus platanoides, 

 Populus tremuloides, Quercus ellipsoidalis, Hicoria ovata, 

 Quercus velutina, Populus grandidentata, and some gnarly 

 specimens of Quercus macrocai*pa of irregular gi'owth. 

 Ostrya virginiana is very abundant. The undergrowth is 

 notable chiefly from the great variety of shrubs rather than 

 from particularly characteristic species. Most of the shrub 

 species of the region are present. The ground cover con- 

 sists of mesophytic herbs, such as Asarum canadense, Viola 

 spp., Hepatica spp., Sanguinarea canadensis, and many 

 others. Mesophytic ferns are in great abundance. About 

 the edges and in openings of these woods there are in- 

 vaders of a xerophytic or xero-mesoph>i:ic sort, such spe- 

 cies, for example, as Euphorbia corollata, Helianthus hir- 

 sutis. Verbena angustifolia, Eupatorium urticaefolium, 

 Campanula americana. 



The Heckman woods on the east shore of the Rock just 

 north of Oregon also exhibit in spots the climax form of 

 the region. Here again Quercus alba is the dominant tree 

 species. Quercus rubra is here, however, almost as im- 

 portant. Other tree species are Hicoria ovata, small 

 Fraxinus americana scarcely over five feet in height, Pru- 

 nus serotina, Quercus ellipsoidalis, Q. velutina, Juglans spp. 

 Acer saccharum, although present, is not yet of any im- 

 portance in the tree community. The frequent occurrence 

 of species like Hicoria ovata, Quercus ellipsoidalis and Q. 

 velutina, when taken in conjunction with the more meso- 

 phjiiic undergrowth and the quite mesophytic ground cover, 

 indicate clearly that the succession, while advancing to- 

 wards a mesophytic climax, has not yet reached a full ex- 

 pression of this, since Acer saccharum is negligible and even 

 absent yet in parts. In the more mesophytic undergrowth 

 are such shrubs as Hamamelis virginiana, Xanthoxylon 

 americanum, besides the less representative species of the 



