24 NEW YORK STATE MUSEUM 



waves have very little effect. This growth of plants retards the 

 motion of the water, so that any sediment which may be in the 

 water is depositedj and at the same time the shore is not sub- 

 jected to the beating of waves. Under these conditions a fringe 

 of moss springs up and rapidly spreads out over the surface of the 

 water. Just a little in advance of the mosses' a floating mat of 

 cat-tails is usually found, Avhich is an important help in the 

 spread of the moss by furnishing greater protection from the 

 waves than is given by the rushes alone. Though these mosses 

 grow most luxuriantly in such locations, the growing part must 

 be slightly above the water level, and the cat-tails furnish a sup- 

 port on which the mosses grow more rapidly than when alone, 

 because more of the growing part is above the water. 



As soon as the moss has formed a mat over the surface, certain 

 grasses and ferns spring up and add to the deposit of organic 

 material formed by the dead plants. As the mat becomes deeper, 

 heath plants begin to grow and by their more woody stems help 

 to make a more porous deposit, oni which larger bushes take root. 

 As soon as the mat becomes deep enough to reach the bottom of 

 the lake near the shore, the deposit gradually rises above the 

 level of the waters of the lake, and small trees find suitable con- 

 ditions for their growth. The effect produced by the trees and 

 bushes is to form clumps of vegetation above the general level of 

 the moss, so that many trees which ordinarily are not supposed 

 to endure such moist conditions grow in luxuriance. 



Such a bog in time will entirely cover the lake, and the zone of 

 rushes and water lilies will be the first to be eliminated, then the 

 cat-tails disappear, and the moss and other plants will occupy the 

 entire surface. In the center of the lake a quaking bog will be 

 left ; but, by the gradual filling both by pressure from the growth 

 of the lateral deposits and by the deposition of decomposed parti- 

 cles from the overlying vegetation, the bog becomes a solid mass 

 of peat. As soon as this occurs, the level of the entire bog be- 

 gins to rise, and the spread of bushes and trees over the entire 

 surface is very rapid. 



