THE DECIDUOUS FOBEST CLIMAX. 185 



torically, though it was made without reference to succession. Ganong (1891) 

 has described in detail the large Sphagnum bogs of New Brunswick: 



These are composed of pure Sphagnum and have their centers raised many 

 feet above the margins. The one visited is perhaps half a mile in length and 

 less than one-sixth as broad. It rises gently from the margin all aroimd to a 

 height of about 10 feet, sloping more gently for 4 or 5 feet more, above which 

 it is flat-topped. The surface is entirely without trees and shrubs except for 

 a much-dwarfed blueberry. The bog is composed of nearly pure Sphagnum 

 free from all roots and showing no decay or anything resembling muck. A few 

 other mosses and lichens occur on the surface, but appear to have no part in 

 the peat formation. The bog is firm and does not tremble underfoot. On the 

 one side it is boimded by high land and on the other slopes down into an ordi- 

 nary bog containing spruces and ericaceous shrubs. The writer explains the 

 development of the bog by the prevalence of large, cold, clear springs. The 

 absence of trees and skrubs seems to be due to the coldness of the water, and 

 is attested by the fact that the boreal Chamaemorus grows in great abundance. 



Pieters (1894 : 9) has reached the following conclusions as to the vegetation 

 of Lake St. Clair, Michigan: 



1. The flora is arranged in more or less well-marked zones limited by 



the depth of the water, and having certain plants characteristic 

 of each zone. 



2. The shallow water and the gradual slope of the bottom give rise to a 



somewhat mixed flora. 



3. The Characetum covers the bottom throughout that part of the lake 



studied. 



4. The distribution of the plants is dependent primarily upon the depth 



of the water. 



5. The distribution of the Characeae is dependent also upon the char- 



acter of the bottom, a sandy bottom being unfavorable and a clay 

 or alluvial one favorable to their groAvth. 



In a later paper upon the plants of western Lake Erie (1901 : 67), the author 

 finds the zonation so interrupted and confused as to make the recognition of 

 different zones imdesirable. 



Ganong (1897 : 137) has summarized the development and structure of 

 raised bogs in New Brunswick as follows: 



The flora of the peat-bogs is on the whole very similar to that of the Hoch- 

 moore of Europe. Sphagnum, Eriophorum vaginatum, Scirpus caespitosus, 

 Ruhus chamaemorus, Andromeda polifolia, Vacdnium oxycoceus, and V. vitis- 

 idaea are common to the bogs of both, while Ledum palustre is represented by 

 L. latifolium and Vacdnium myrtiUus by V. caespitosum, canadense, and 

 pennsylvanicum. The floras differ in the absence of Calluna vulgaris. Erica 

 tetraliXjPinus pumilio, Salix repens, etc., in American bogs, and by the char- 

 acteristic presence of Kalmia, Cassandra, Gaylussacia, Larix am^icana, and 

 Picea nigra. 



The raised bogs are surrounded by a dense spruce forest which they are 

 overwhehning. The high parts of the bogs are made up of Sphagnum bearing 

 scanty dwarf trees and shrubs. The hummocks are typically covered by 

 Empetrum nigrum and Polytrichum, while the hollows are filled with large 

 lichens. In the wetter places, Eriophorum vaginatum and Scirpus caespitosum 



