486 A TEXTBOOK OF BOTANY [On. XI 



replaced after fertilization by the long-stalked rounded spore 

 capsules. These stalks, while apparently identical with 

 those of true Mosses, have a very different morphological 

 origin, for they are developed by the gametophyte. The 

 spores are disseminated by wind, and germinate in wet 



places to a small thallus-like 

 protonema, on which the new 

 leafy Sphagnum originates 

 from a bud. 



The Peat Mosses develop 

 especially well in shallow shel- 

 tered ponds. From the shores 

 they grow outward in a mat, 

 which at first floats, but later 

 becomes compacted and sunken 

 by the continuous upward 

 growth of the Mosses and other 

 plants which associate them- 

 selves therewith. The poor 



FIG. 345. Leaf of Sphagnum ; , . , , 



x 60 Q. drainage in such places per- 



Above, cross section, showing the m its accumulation of Organic 

 smaller chlorenchyma and larger ., ,., , ,,, .,., 



water cells, the latter with capillary acids which check the activity 



openings. Below, surface view. o f decay-causing Molds and 



(Adapted from Sachs.) . ,-. i , 



Bacteria; and thus the dead 



remains of the Mosses, with roots and rootstocks of 

 associated plants, accumulate until the basin is filled 

 and the pond disappears. This is the way in which the 

 peat bogs, so characteristic of high northern regions, 

 are formed; and after the same general manner, but 

 with different plants, the coal beds were formed in the 

 swamps of the Carboniferous era. More than this, the 

 Peat Mosses, by virtue of their great power of water absorp- 

 tion, can actually grow a dozen feet or more above the ori- 

 ginal level of the pond, thus forming remarkable raised 

 bogs. These are treeless, and bear only small shrubs and 

 other low-growing plants. 



