198 A NATURALIST IN THE GREAT LAKES REGION 



horsetail (Fig. 234) and on the drier parts of the sedge mat the 

 swamp fern, Aspidium Thelypteris (Fig. 235). 



Shoreward from the sedge zone is a zone in which the ground 

 stratum is marked by an abundant growth of sphagnum moss 

 (Fig. 236) above which is a shrub stratum with a striking group of 

 xerophytes, the most conspicuous of which is the leatherleaf, 

 Chamaedaphne calyculata (Fig. 239). The zone is usually called 

 the cassandra zone. Sphagnum is a pale green moss whose 

 spongy tissue holds with tenacity an immense bulk of water. 

 It forms a soft carpet, often a foot deep. Below it the peaty 

 soil lies to a depth of several feet usually saturated with water 

 and very cold. The soil temperature will be in the neighbor- 

 hood of 50 F. in midsummer, even on days when the air tem- 

 perature is around 100 F. 



Growing in the sphagnum one finds such orchids as Arethusa 

 (Fig. 229), the ragged orchis (Fig. 237), fragrant ladies'-tresses 

 (Fig. 238), together with cranberries, both large and small, cot- 

 tony grass, and, most striking of all, the pitcher plant. This 

 latter is another of the queer insectivorous plants found in this 

 bog region. Its vase-like" leaves which spring in clusters from 

 the central root are 8 or 10 inches long and are lined with slippery 

 hairs pointing down. The lip of the vase bears a ridge of succu- 

 lent tissue on which numerous insects feed with avidity. In their 

 eagerness they sometimes slip off into the pitcher which is partly 

 filled with water. To crawl back against the sharp pointed hairs 

 is not easy. So the bottom of the pitcher usually contains a 

 more or less concentrated "insect soup" that is absorbed by 

 the plant and serves as food (Fig. 240). 



In the shrub zone besides the leatherleaf areiound Andromeda, 

 chokeberry, low birch, and other shrubs of similar character. 

 Andromeda (Fig. 241) is a low evergreen shrub with narrow 

 leaves that have their edges rolled back and the under sides of 

 the young leaves covered with a white varnish. The urn-shaped 

 corolla is pink, sometimes white. The flowers are in small clus- 

 ters (umbels). 



