58 Studies in Forestry [CHAP. in. 



supplies of assimilated nourishment offered under the above 

 circumstances to the upper portion of the bole than to the 

 under part. 



In the earlier stages of development the age of the crop is 

 of little practical importance. All species of trees, when grown 

 in woods of normal density, assume a conical or spindle-shaped 

 crown till they outgrow the pole stage and become tree-forest ; 

 but, having passed through the most active period of their growth 

 in height, they then begin to exhibit their natural tendencies 

 more distinctly. Thus Larch, Spruces, Douglas Fir and Silver 

 Firs continue to develop more vigorously upwards than side- 

 wards ; Pines, Elm, Beech, Maple, Sycamore, Birch, sessile Oak, 

 Ash, and Alder begin to assume an oval crown ; whilst English 

 Oak and Hornbeam get rounded off with a broad, obovate crown. 

 As they approach the limits of age of healthy vigorous growth, 

 all trees, except Larch, Spruce, and Douglas Fir, assume 

 a blunted or rounded off growth near the summit, due to the 

 growth in height declining sooner than the lateral expansion. 



So far as soil and situation affect the shape and habit of 

 growth, fresh, fertile loams stimulate to full-foliaged coronal 

 development and large girth of bole, though somewhat at the 

 expense of its length. Deep, fresh, light sandy soils favour 

 length of stem ; but, as the crowns are thinner, and the branch- 

 development is sparser, the girth consequently remains less. 

 Shallow and rocky soils affect the stem-development very 

 prejudicially, and cause branching growth and excessive root- 

 systems spreading far around in search of moisture and nutri- 

 ment. Great elevation above sea-level, and raw, cold exposures, 

 militate against the formation of good stems. In Scotland, 

 at 2,500 ft, the Scots Pine is more like a shrub than a tree. 



The conclusion deducible from the above facts is that wood- 

 land crops formed of shade-bearing genera able to thrive with 

 a small growing-space, i.e. Beech and Hornbeam, but more 

 particularly Spruces, Silver and Douglas Firs, are able to main- 

 tain close canopy better and longer than woods formed chiefly 



