NATIVE VEGETATION. 183 



growth; the Ericacece form the chief undergrowth, and the Sphag- 

 noid mosses carpet the peaty bottom, forming a well-marked flora. 



CLASS XIII. The Arbor Vitce Group. This is similar to the last 

 save that the Arbor Yitse, or White Cedar, as it is frequently called 

 (Thuja occidentalis\ takes the place in whole or in part of the Tama- 

 rac. Usually the Tamarac is present in greater or less numbers. A 

 not unfrequent arrangement consists of a predominance of the Arbor 

 Yitse around the borders of the swamp, and of the Tamarac toward the 

 center. The latter is a more thoroughly swamp species (although oc- 

 casionally seen on the hillsides) than the former. 



CLASS XIY. The Spruce Group. This is similar to the two pre- 

 ceding groups, except that the Black Spruce (Abies nigra) is the chief 

 arboreal form. The Larch and Arbor Yitee are frequently present. As 

 the Spruce is confined to the northern regions, more of the northern 

 forms of minor vegetation are associated with this group, although 

 the same tendency is shown in the other classes in the same latitude. 



From the habit of these three paludal conifers of mingling, it is 

 sometimes difficult to classify a given swamp, and it has not been 

 thought important to distinguish them on the accompanying map of 

 vegetation, although they were so distinguished on the original map. 



C. GROUPS INTERMEDIATE BETWEEN THE UPLAND AND MARSH 



GROUPS. 



CLASS XY. The Slack Ash Group. In this, as the name implies, 

 the Black Ash (Fraxinus sambucifolia] is the predominating plant. 



The Black Alder (Alnus incana) is a subordinate and quite constant 

 associate, and the two characterize the group. The Arbor Yitse is fre- 

 quently present, and sometimes the Witch Hazel. Otherwise, as far as 

 observed, the association is not constant. 



CLASS XYI. The Yellow JSirch Group. This is not altogether a 

 well defined group. The abundance of Yellow Birch (Betula lutea, 

 excelsa) is the most marked feature of the vegetation. The Hemlock 

 is very common, and the Maples and Beech are present. Under the 

 dense shadow of these, several species of Lycopodium, the Dwarf 

 Yew (Taxus Canadensis], the large Purple-flowered Easpberry (Rubus 

 odoratus\ the Ericaceae (Pyrola rotundifolia and secunda\ the Co- 

 hosh (Actea spicata, var. alba) abound among others, though the 

 most of these are present in other groups. This group occupies only 

 some limited areas in the peninsula east of Green Bay, and in the 

 press of other duties, sufficient opportunity was not afforded for satis- 

 factory study. 



