58 BRITISH MOSSES. 



has grown, years after years, and if it has not destroyed 

 the old trees it has prevented the growth of young ones. 

 The stools of the trees buried in the antiseptic waters of 

 the Sphagnum pools have been preserved, whilst the fallen 

 trunks have, except when preserved by the like circum- 

 stance, rotted, and added their remains to the peat which 

 the Sphagnum has been producing. It has been observed 

 in several places in Scotland, that the under side of fallen 

 trees which would be protected from decay by the tannin 

 of the Sphagnum is preserved, whilst the upper side has 

 decayed or rotted away. Year by year the process of decay 

 on the lower parts of the Sphagnum went on until the 

 water grew shallower and at last disappeared, leaving the 

 original morass choked and filled up by the Sphagnum and 

 the plants which it has nourished. On the top of this soil 

 have grown first the heath and bog shrubs which first 

 succeed the Sphagnum, and in time, as the soil has grown 

 more solid, forest trees. This is our second forest. This 

 first peat deposit, or the lower part of it at all events, 

 having been turned into the black peat impervious to water, 

 plays the same part in the second stage that the clay or 

 pan did in the first stage. Again, the drainage of this 

 second level got stopped, and the forest bottom loaded with 

 stagnant water, the home of the Sphagnum ; together, the 

 water and the Sphagnum killed the forest trees, which 

 share the fate of their predecessors. The same history is 

 gone through again the Sphagnum filling up the morass 

 and turning the water into dry land until it supports the 

 third forest. 



Decay of the Moss. There comes, however, in many 



