1905] TRANSEAU BOGS OF THE HURON RIVER VALLEY 363 



but the blue-green algae may be present up to the water's edge, in 

 such situations frequently forming marl pebbles. The lower limit 

 of existence is largely determined by the transparency of the water, 

 and may lie between 20 and 30 feet (6-9 m ). Of the littoral plant 

 associations there are commonly two quite distinct divisions, the 

 outer made up largely of submerged or floating pondweeds and water- 

 lilies, the inner of half -submerged rushes and sedges. Both are con- 

 cerned in the process of peat formation. Under such conditions 

 there naturally develop, in regions of calcareous underground waters, 

 an outer zone of chara dominance and marl deposition, and an inner 

 zone of pondweed-sedge dominance and peat deposition. Varia- 

 tions in the slope of the bottom, in the amount of wave action, in the 

 presence of shore currents, and in the color of the water, determine 

 whether one or both of these processes shall go on, and to what 

 extent these activities are kept distinct or grade into one another. 



In the case of the peat, however, the process is not dependent 

 upon water species alone. They act merely as forerunners of a 

 denser and more luxuriant vegetation which frequently is of greater 

 quantitative importance. Briefly, we may note here that in the case 

 of the bogs, unlike that of the swamps, the plants which develop on 

 the margin, especially Carex filijormis and forms of Eriophorum, 

 are able to secure all of their food materials from the water and air 

 and build their own substratum. This tangle of roots and rhizomes 

 usually attains a thickness of several inches, and on account of its 

 low specific gravity floats on the surface of the water. Upon this 

 foundation the sphagnum and bog shrubs advance, adding their 

 quota to the debris. Later, these are followed by such tree forms as 

 the tamarack. Coincident with this increased weight and augmented 

 rate of deposition, comes the progressive submergence of the floating 

 substratum, and its gradual disintegration and humification. The 

 accompanying fig. 4 will serve to illustrate this process. 



Within the last two years much has been promised toward the 

 utilization of the peat deposits in this region for fuel purposes. Com- 

 panies have been organized, and the machinery necessary for the 

 drying and consolidating of the peat has been much improved. At 

 Capac and Chelsea, factories have been erected, and attempts are 

 being made to place the industry on an economic basis. If these 



