176 ILLINOIS STATE ACADEMY OF SCIENCE 



region, such as Cornus, Ribes, Ampelopsis, Toxylon, Rubus, 

 Rhus, Vitis, Pyrus. Some small trees, but a few feet in 

 height, of Fraxinus quadrangulata are present. The 

 ground cover is much the most advanced layer, affording 

 the best indication of the approaching mesophytism of the 

 other strata of the vegetation. Here are such herbs as 

 Thalictrum dioicum, Polygonatum spp., Trillium spp., Po- 

 dophyllum peltatum, Arisaema triphyllum, Caulophyllum 

 thalictroides, and so on. There is a fair assemblage of 

 mesophytic ferns, Aspleniums, Aspidiums, but not so great 

 a display as in the McCormack woods. In this connec- 

 tion it must be noted that here the topography often, even 

 where the mesophytism has advanced to the point just de- 

 scribed, furnishes no especially favorable conditions for 

 mesophytism. There are, to be sure, spots where topo- 

 graphic conditions give mesophytic sites, but this area of 

 the Heckman woods has advanced well as a whole towards 

 the climax, and evidently from much less mesophytic oak 

 woods phases of the succession. It has, apparently, been left 

 for some years without noticeable disturbance by grazing or 

 other factors that make for retrogression. The younger 

 tree growth is represented by such species as Fraxinus 

 americana, Prunus serotina, Ulmus spp., Juglans spp,, and 

 Hicoria minima, clearly indicating an advance beyond the 

 older tree stand of Quercus alba, Q. ellipsoidalis, Q. velu- 

 tina, Hicoria ovata. There is evidently greater soil mois- 

 ture throughout this whole woods than in the ordinary up- 

 land woods of the region, and this greater quantity appears 

 to result from the presence of the dense stand of the wood- 

 land rather than from any especially favorable topographic 

 arrangement. In some parts of the area Tilia americana, 

 Acer saccharum, Quercus acuminata, Q. alba, Juglans nigra, 

 J. cinerea, Quercus rubra, Hicoria minima, Robinia pseu- 

 dacacia, occur. The Acer saccharum, though small, still 

 proves clearly what the future of the succession will be if 

 the vegetation continues to be left undisturbed. 



The Cartwright woods on the west shore of the Rock 

 north of Oregon, while in places a much confused assem- 

 blage of telescoped and condensed stages, nevertheless ex- 

 hibits the oak-maple climax form excellently over some of 



