CHAP, ii.] The British Sylva 37 



not in Britain of sufficient technical and commercial value to 

 lead to their cultivation on any large scale ; but among them 

 the Beech and, on moister varieties of soil, the Hornbeam are 

 of great sylvicultural importance as the ruling species or matrix, 

 either in the shape of underwood or of tree-forest, along with 

 which the more valuable classes of timber trees, Oak, Ash, 

 Maple, Sycamore, Birch, &c., may be most profitably grown on 

 localities where the soil would be liable to deterioration if the 

 woods consisted of these thinly-foliaged and light-demanding 

 species only. 



For the formation of woods of normal density or full leaf- 

 canopy the number of individuals per acre varies, as has already 

 been stated, according to the species of tree ; but wherever 

 reliable data have been collected, it appears that, on soils of 

 the best quality for the requirements of each genus of tree, 

 at the age of 120 years there are 37 % more Beech, 24^ % 

 more Silver Fir, and 60 % more Spruce than individual stems 

 of Scots Pine per acre. It also appears that at all ages 

 there is on soils of the best quality invariably a very much 

 smaller number of individual trees of any particular species than 

 on the poorer classes of soil. The difference may often be 

 enormous, for at eighty years of age Scots Pine woods on the 

 best class of Pine soil consist of only one-third of the number 

 of trees that are generally found on the poorest class of soil. 

 So far as these different results are concerned, with one and 

 the same species of tree, they are explainable through the 

 fact that the general development and the natural process of 

 selection of the fittest the struggle for light and air, for domina- 

 tion, and for individual existence is more energetic and 

 decisive on good soils than on those of inferior quality. The 

 differences exhibited by the various species of trees, however, 

 is dependent on their different sylvicultural characteristics 

 with regard to the natural development of their crowns, and 

 their special requirements as to growing-space. Through- 

 out the Spessart forest it has been found that the following 



