CHAP, in.] Characteristics of Trees 59 



of Larch, Pines, Ash, Maple, and Sycamore. And when, as 

 in the case of Oak, Birch, and Chestnut, a tendency to branch- 

 ing growth is combined with strong demands for light, the 

 leaf-canopy is apt to be interrupted early and to an injurious 

 extent; and the natural impulse in this respect is all the 

 greater, the less favourable the soil and situation may be for 

 the particular species of tree in question. 



V. Increment, or Rate of Growth in Height, 

 Girth, and Cubic Contents. 



Growth in height varies, both in energy and duration, accord- 

 ing to the species and the age of the tree, the soil and situation, 

 and the methods of formation and treatment of the woods. It 

 is most active in Douglas, Spruce, and Silver Firs, Larch, Scots 

 and Weymouth Pines, which can attain an average height of from 

 110-140 ft. the Douglas Fir grows to over 300 ft. in height, 

 and 1 8 ft. in girth, in its home in North America; Oak, Ash, 

 Beech, Maple, Sycamore, and less frequently Elm, Poplar, and 

 Birch reach a height of 100-130 ft. ; whilst Black Pines, Horn- 

 beam, Alder, and Willow are seldom over 80-100 ft. high when 

 mature. These data are only for crops of normal density. 



But the maximum heights usually attained by the various 

 species of trees are reached in different periods of time. This 

 fact, combined with their varying demands as to light, is of 

 immense importance from the practical sylvicultural point of 

 view ; as these are two of the main points to be considered 

 (when once the protection of the productive capacity of the 

 soil has been duly safeguarded) with regard to the formation 

 and tending of mixed woods. 



Birch and Larch, above all others, then Poplar, Alder, Ash, 

 Maple, Sycamore, Elm, Willow, Weymouth and Scots Pines, 

 and Douglas Fir, are the trees that shoot up most rapidly 

 during their youthful period of growth; whilst Oak, Beech, 

 Hornbeam, and Black Pines may be classed as of moderately 



