772 FOREST-LITTER. 



In Scots pine and larch woods, moss is generally an un- 

 important factor in the soil-covering, or may be completely 

 absent. Hunger-moss, or Iceland-moss (Cetrana) is a lichen 

 and denotes great poverty of soil. 



As regards age, in the early years of dense spruce and 

 silver-fir forests, there is only a slight production of moss ; 

 after the leaf -canopy has become elevated, so as to admit suffi- 

 cient light to the soil and allow for a slight movement of air- 

 currents, moss gradually spreads over the ground. It then 

 continually becomes denser and deeper the higher the leaf 

 canopy, and attains its maximum in mature woods which have 

 been already thinned and contain advance-growth,* provided 

 the soil continues moist. 



The system of management affects the growth of moss, in 

 so far that uneven aged woods, resulting from natural regene- 

 ration by seed, are generally more favourable for the produc- 

 tion of moss than even-aged and artificially formed woods. 



"Wherever the growth of moss is luxuriant, it regenerates 

 itself after removal for litter more rapidly than under 

 opposite conditions. If the moss has been completely 

 removed, an interval of 3 to 5 years passes before it is repro- 

 duced, and this may be longer on poor soils. 



3. Litter from Weeds. 



The forest weeds, which are used chiefly as litter, are 

 heather, broom, Genista and ferns : less frequently bilberry- 

 bushes (Vaccinium Myrtillus) and other species of Vaccinium, 

 reeds, grass, etc. 



Heather, chiefly ling (Calluna vulgaris), [but in Britain, also 

 bell-heather (Erica cinerea) and cross-heather (E. Tetralix). 

 Tr.] produces a sour, partly-decomposed humus, which when 

 the soil is dry, resembles charcoal-powder, but when the soil 

 is wet, forms a moist mass ; heather predominates on open 

 sunny localities and on poor silicious soils, where it spreads 

 freely and produces peaty heather-humus. The removal of 

 the heather with the sods of humus, that are full of its roots, 



* Advance -growth. The seedling underwood sj.ringing-iip in a high t'oiv>t. 



