178 GEOLOGY OF EASTERN WISCONSIN. 



rus Goronaria), the Wild Black Cherry (Prunus serotina), the Choke 

 Cherry {Prunus Virginiana), and the Wild Plum {Prunus Ameri- 

 cana), represent the Eosacese. The Sumac {Rhus typhina) is com- 

 mon, but not significant, as it is a member of other groups. 



The attendant underbrush is equally characteristic. The Hazel- 

 nut {Corylus Americana) is almost everywhere present with this 

 group, though rare or wanting in connection with the others. The 

 Panicled Cornel {Oornus jpamiculata) is very common, and with the 

 Hazel constitutes the chief underbrush. The Wild Eed and Black 

 Easpberries {Bubus strigosus and occidentalis) and the High-bush 

 Blackberry {Rubus villosus) are all present, but seem to prefer asso- 

 ciation with the other groups. 



If we descend to the herbaceous vegetation beneath, similar facts 

 will be found, but it would transcend the brevity desirable in this 

 report to enter fully into the details. And there is this further rea- 

 son for not doing so in this connection, that many of these plants are 

 more dependent upon the conditions furnished by the overshadowing 

 vegetation, than upon the nature of the soil, and are therefore less 

 instructive as to agricultural questions. 



This group as here constituted includes both the " Oak openings" 

 or " Oak orchards," and the denser oak forests. There are sufficient 

 reasons, however, for separating them into two classes, as they indi- 

 cate different, though allied, agricultural capabilities. The oak open- 

 ings are most nearly related to the prairies, while the oak forests 

 graduate towards the following classes. Those plants which have been 

 mentioned as preferring association with the subsequent groups, as the 

 Pignut Hickory, G-reat-toothed Poplar, etc., are found chiefly in the 

 forests, and much more rarely in the openings, while of the species 

 common to the prairie and oak groups, the majority are only found 

 in the openings, and but few in the denser oak forests. 



Glass III. The Oak and Maple Oroiip. It is difficult to draw 

 sharp lines of demarkation between the several classes of heavy forests, 

 and to circumscribe the areas occupied by each. The fact is, that no 

 abrupt line of separation exists. But perhaps the distinctions here 

 atteiupted are as clear and as legitimate as in many other departments 

 of science, where such distinctions are sanctioned, and for the practi- 

 cal ends for which this investigation is made, it is essential that such 

 divisions should be attempted, and besides the tout ensemUe is dis- 

 tinct, though the constituents may be linked into the groups on either 

 hand. These observations seem especially demanded as an introduc- 

 tion to the definition of this class. The oaks which have been made 

 the most conspicuous characteristic of the preceding group are made 



