MICHIGAN ACADEMY OF SCIENCE. 
55 
Fig. 1.—Independence and Mud Lakes, showing present distribution of plants. 
I—Independence Lake. 
L—Mud Lake. 
A—Peat deposit. 
B—Open water. 
O—Old Lake shore. 
P—Present lake shere. 
and black spruces; third, the zone of Cassandra and Sphagnum; fourth, 
the zone of floating plants, and fifth, the zone of water plants. Under 
the head of marginal zone is included all that part of the bog which 
lies next to the shore and which now shows no signs of ever having borne 
tamaracks. Its plant societies are intermediate between those growing 
upon the mineral soil on one side and the typical bog societies on the 
other. The majority of its plants, however, are from the mineral soil 
societies. The width varies from fifty to four or five hundred feet. The 
principal societies in the marginal zone are, (a) the marsh-grass mea¬ 
dow society, (b) the cat-tail society, (c) the willow society, and (d) 
