Mosses and Peat 



and there deep pools of liquid black mud at least four 

 feet deep, into which one's foot is apt to slip. On the 

 top of the hillocks the drying influence of the wind 

 or of sunshine in a dry summer, hampers the growth 

 of the Sphagnum, and perhaps a few plants of Poly- 

 trichum or an adventurous heather seedling succeed 

 in establishing themselves. Now begins a struggle 

 for water between the Sphagnum and the heather 

 roots. 



Should strong winds and a dry summer or two 

 favour the growth of the latter, the roots will colonise 

 the summit of the Sphagnum hillock and proceed to 

 gradually kill out the moss all round them. The 

 upper surfaces of all the hillocks may in that case 

 become dry crumbly peat occupied by heather and 

 masses of grey and white lichens with perhaps a few 

 other plants. These heather plants are, however, separ- 

 ated by an irregular network of living moss, deep mud 

 holes, or possibly irregular water-courses full of various 

 sedges and marsh plants. 



If the conditions are favourable, the whole surface 

 of the moss will become dry dead peat, in which the 

 heather, blaeberries, oxycoccus, &c., are growing vigor- 

 ously. As soon as that happens, if sheep and cattle 

 are excluded, seedling Scotch firs and birches begin to 

 overgrow the moss, and quite a forest might develop 

 if the neighbouring villagers would leave it alone. 



Such a Scotch fir forest was actually formed over 

 most of the Scottish uplands (see p. 225). 



But it is not always the heather that wins the day ; 

 should the outlet of the little streams which leave the 

 moss be choked up, then the Sphagnum of a hillock 

 would gradually grow up over the heather stems and 

 suffocate it. 



On flat places, as, e.g. 9 where peat has been cut and 



75 



