CUMULOSE DEPOSITS 308 



other kinds of plants, making meadows and forests. In other 

 cases when basins of stagnant water are too deep for vegetation 

 of aquatic plants, nature attains the same result by a different 

 special process; namely, by the prolonged vegetation of certain 

 kinds of floating mosses, especially the species known as sphagna. 

 These grow with prodigious speed, and expanding their branches 

 in every direction over the surface of ponds or small lakes, soon 

 cover it entirely. They thus form a thin floating carpet, which 

 as it gradually increases in thickness serves as a solid soil for 

 another kind of vegetation, — that of the rushes, the sedges, and 

 some kinds of grasses, which grow abundantly mixed with the 

 mosses, and which by their water-absorbing structure furnish 

 a persistent humidity sufiBcient for the preservation of their 

 remains against aerial decay. The floating carpet of moss be- 

 comes still more solid, and is then overspread by many species 

 of larger swamp plants, and small arborescent shrubs, especially 

 those of the heath family; and so, in the lapse of years, by the 

 continual vegetation of the mosses, which is never interrupted, 

 and by the yearly deposits of plant remains, the carpet at last 

 becomes strong enough to support trees, and is changed into a 

 floating forest, until, becoming too heavy, it either breaks and 

 sinks suddenly to the bottom of the basin, or is slowly and grad- 

 ually lowered into it and covered with water. "^ 



It is to such processes that are due, in large part, the inland 

 swamp soils of many localities. Beginning at and near the 

 shore and upon a soil of wet sand, the organic matter has accu- 

 mulated year by year till now several feet in. thickness and in 

 some cases covering miles of territory. The proportion of or- 

 ganic matter in such a deposit naturally increases from the shore 

 outward until in the upper and central layers it may comprise 

 90% of the total weight. 



This feature is well brought out in the following analyses 

 of material from an open ground prairie swamp in Carteret 

 County, North Carolina. 



^Geol. Survey of Pennsylvania, 1885, p. 106. Tlie water hyacintli so 

 prolific in the sluggish streams of Florida, would, in time, doubtless pro- 

 duce similar conditions. 



