i 9 o 5 ] TRANSEAUBOGS OF THE HURON RIVER VALLEY 373 



alteration. They were originally strongly cuticularized, and this has 

 aided in their preservation. The color is commonly a pale yellowish- 

 brown. During life these plant materials become strongly matted 

 and interwoven, and this structure frequently persists. It is this 

 structure that gives to the Carex-Eriophorum zone in many lakes its 

 strength to support heavy bodies. A man's weight will carry the 

 substratum a foot beneath the surface of the water, but it seldom 

 breaks under the strain. In the case of lakes where this zone is 

 unusually developed, it may cover a large part of the lake surface and 

 be of great importance in the filling in of peat. In such cases the 

 deposition takes place largely by the gradual falling of material from 

 the under side of the floating substratum. On account of the slight 

 weight of the material, it does not descend and produce a compact 

 deposit on the bottom, but forms a sort of thick liquid peat. 



The sphagnum- shrub zone, where well developed, usually shows a 

 brown peat beneath it. It is composed largely of sphagnum and the 

 semi-decayed twigs, rhizomes, and leaves of the other, plants. It is 

 distinctly fibrous, but of a type different from that of the sedge zone; 

 the fibers are short, and the material is not nearly so tenacious. 



Under the tamaracks a large part of the annual peat increment is 

 made up of the tamarack needles, though mosses (Hypnum, Sphag- 

 num, and Polytrichum) usually are of importance in this connection. 

 The color is reddish-brown and darker than that of the shrubby 

 zone. The fibrous structure is still less apparent, though present. 



When these bogs have been burned over and partially drained, 

 there frequently comes in a dense ground covering of moss (Poly- 

 trichum). In such cases the peat continues to accumulate, largely 

 through the agency of this plant. In such situations the peat is a 

 reddish-brown, and the plant structures have practically disappeared 

 through decay. Below the upper layer, the peat when moist has the 

 sticky, clayey properties of well-decomposed peat. 



One other well-marked stage is shown in the areas of muck land 

 now under cultivation to onions and celery. Under the influence of 

 drainage and tillage, the disintegration is nearly complete. All plant 

 structures have disappeared, the humous acids have been largely 

 neutralized or washed out, and there is left only a fine, powdery, 

 brownish-black "muck." 



