NATIVE VEGETATION. 181 



nigra) wanders away from its marshy habitat, and the Arbor Vitae 

 extends itself quite freely upon the uplands. 



CLASS VII. Pine Group. This includes the well known vegeta- 

 tion of the "Pine Lands." It is here made to include those regions 

 over which the pine is predominant in distinction from those in 

 which it is simply scattered through prevailing hardwood timber, as 

 in the preceding group. The leading tree is the Pinus strobus. 



CLASS VIII. Limestone Ledge Group. This is a small but inter- 

 esting vegetal cluster, covering limited areas in which there is the 

 most meager soil, resting upon limestone. In this heavy drift region, 

 such areas are few and small, but the distinctness of the flora is so 

 marked, and so well illustrates the fundamental principle upon which 

 the value of all these observations rests, that it merits a name and 

 place as a separate class. The Poplars (Populus tremuloides, grandi- 

 dentata, and balsamifera), the Canoe Birch (Betula papyracea), the 

 Snowberry (Symphoricarpus racemosus], the Smooth Sumac (Rhus 

 glabrd], with the Conifers, constitute the major vegetation, and rather 

 from the combination than from the constituents, cause it to stand 

 out in. marked contrast to the heavy timber by which it is fre- 

 quently encompassed. It forms a thicket rather than a forest. 

 The most characteristic feature is the abundance of the Poplars and 

 the Birch. 



The Populus tremuloides is not common in the forests by which 

 the typical areas of this class are surrounded, which makes its abund- 

 ance here the more conspicuous. 



The Rubus strigosus, Cornus circinata and Lonicera parviflora 

 are attendant shrubby plants. The herbaceous vegetation is also 

 peculiar. 



CLASS IX. The Comprehensive Group. This class consists of a 

 commingling of nearly all the arboreal species of the foregoing groups. 

 Clusters may be selected that are representatives of nearly all the 

 other classes, but in general the species are curiously mingled, and do 

 not array themselves in the definite associations that characterize the 

 preceding groups. It is most nearly allied to the Maple, Beech and 

 Conifer group, and lies contiguous to it, and near the limit of marked 

 lake influence. 



B. MARSH VEGETATION. 



CLASS X. The Grass and Sedge Group. This includes the well 

 known occupants of our open meadow .marshes. It corresponds to 

 the prairie group among upland vegetation, and in many cases gradu- 

 ates imperceptibly into it. It embraces several subordinate groups 



