166 ILLINOIS STATE ACADEMY OF SCIENCE 



as Acer saccharum, A. nigrum, Tilia americana, Prunus se- 

 rotina, Hicoria minima, Juglans cinerea, J. nigra, Fraxinus 

 americana, Quercus alba, Q. rubra. The following shrubs 

 are rather typical of the undergrowth — Viburnum denta- 

 tum, V. lentago, Staphylea trifoliata, Hamamelis virginiana, 

 and, sparingly, both Amelanchier canadensis and Carpinus 

 carolianiana. Some characteristic herbs and ferns are 

 Viola spp.. Podophyllum peltatum, Trillium spp., Sangui- 

 naria canadensis, Asarum canadense, Hepatica spp., Aralia 

 nudicaulis, A. racemosa, Actea rubra, A. alba, with Menis- 

 permum canadense and Amphicaii^a monoica among the 

 lianes; Adiantum pedatum, Osmundas, Aspleniums, Aspi- 

 diums. The oaks are still the dominant trees generally 

 both in point of numbers and of size. The maple element 

 sometimes is represented by trees of good size but they are 

 generally still subordinate in point of numbers. In a sense 

 this is a beginning aspect of a climax form, as an inspec- 

 tion of the list of species named will indicate. The writer 

 believes there is considerable evidence on the ground that 

 goes to show that this form may not be the ultimate ex- 

 pression, under the prevailing climatic complex, but that a 

 still more mesophytic expression may be the real climax 

 form, if the successional development of the vegetation were 

 allowed to take place v/ithout interference. It is specu- 

 lation, of course, to indicate what the ultimate form might 

 be. Since Fagus americana and Tsuga canadensis are ab- 

 sent, even as possible migrants, the beech-maple-hemlock 

 climax of farther east is out of the question. It is con- 

 ceivable, however, and rather probable, that an ultimate 

 association might involve the well-nigh complete elimina- 

 tion of Quercus alba and perhaps of the more mesophytic 

 Quercus rubra, resulting in a maple association. In much 

 of the eastern portion of the middle west of North America 

 a red oak- white oak-hickory association (Quercus rubra- 

 Quercus alba-Hicoria ovata) is the climax. Sometimes the 

 course of the succession to this is likened to that of the 

 country farther east with the exception of the elimination 

 of the easteiTi climax of beech-m.aple-hemlock. The asso- 

 ciation considered here as the climax of the Rock River 

 woodlands region may be termed an oak-maple climax. It 

 is not believed that this is, or would be if left to its natural 



