ii6 BRITISH FOREST TREES 



ture of at least 43 J Fahr., and a mean temperature of 63^ 

 Fahr. during July and August, whilst it can bear without 

 injury a mean temperature during January not lower than 

 20 f Fahr. Localities with great extremes of summer heat 

 and winter cold are less suited for it than for the spruce, 

 and also such as have great atmospheric humidity, although 

 its growth is decidedly better in moderately damp air than 

 in dry localities. Near its lower vertical limit it naturally 

 seeks the cool, moist, gently sloping northern, north-eastern, 

 and south-eastern aspects, whilst towards the upper limit 

 considerations as to warmth necessitate its growth on the 

 sunnier southern exposures. 



In demands as to mineral strength of soil it occupies a 

 position between the beech and the spruce. The richer soils 

 of the older geological formations favour its development, 

 but it is also found forming extensive forests, especially 

 when grown along with spruce, on the better varieties of 

 sand. Cool slopes with limy or clayey soil often show 

 vigorous growth, but the timber is generally somewhat 

 inferior in quality. The thriving of the silver fir is, in 

 short, less dependent on any particular kinds of soil than 

 on a fair amount of moisture permeating deep into the soil 

 and subsoil, and on favourable situations, such as the coombs 

 and hollows, the dingles and dells, and other protected 

 localities in the sinuosities of mountainous tracts and hilly 

 ranges. Whilst dry soil is unfavourable to it, on wet sour 

 land it cannot thrive at all. 



Requirements as to Light. Among the forest trees silver 

 fir ranks first in capacity for bearing shade, even excelling 

 the spruce in this respect to a slight degree, as might be 

 expected from the longer life of the old foliage. This 

 high shade-bearing capacity enables its natural reproduction 

 to be much more easily carried out than might otherwise be 

 the case, as after standing for a long time, first under th e 



