FURKST TREES 141 



instead of rounding off like the crowns of Scots pine and 

 silver fir at advanced ages. 



Its root-system resembles that of the Scots pine, but if 

 difficulties confront the development of a strong tap-root, it 

 possesses considerable accommodative power of throwing 

 out stout side-roots so as to form a heart-shaped system like- 

 that of the silver fir. On shallow or rocky soil it develops 

 many and far-reaching surface-roots like spruce, which 

 utilise every opportunity afforded by cleavage and fissure to 

 penetrate deeper down. Under these latter circumstances 

 the larch makes greater demands on growing-space than 

 when the soil is deep. 



Requirement* as to Soil and Situation. Somewhat higher 

 demands in regard to atmospheric warmth are made by the 

 larch than by its companion in the same region, the spruce. 

 The minimum of total annual warmth believed to be 

 necessary for the attainment of its normal development is 

 estimated 1 at about 3,010 Fahr., which corresponds with 

 the isotherm indicating a mean annual temperature of 

 36*8 Fahr. as its northern limit of growth. Extremes of 

 winter cold are borne by it better than intense heat in 

 summer. The short spring, followed quickly by equable and 

 moderate summer warmth, to which, after a short 

 autumn, the long winter period of rest succeeds, the 

 characteristically Alpine climate, is the natural one in 

 which it thrives best. There it attains its most vigorous 

 growth in the hollows and coombs along the mountain sides, 

 where it has protection from the violence of the storms. 

 The larch can thrive in dry cool mountain air, but its 

 frequent association with the spruce in hill forests proves 

 that a considerable degree of atmospheric humidity is, if 

 not requisite, at any rate rather beneficial than detrimental 

 to its growth and development. When grown in localities 

 1 \Villkomm, Die forstlichc Flora, *5rV., 1887, p. 121. 



