66 BRITISH FOREST TREES 



age, and twenty-five to fifty-two feet at forty years of age, 

 during which time of greatest energy of growth in height 

 the pine surpasses most other trees of the forest, annual 

 shoots of two feet in length throughout all the dominating 

 poles being common enough on good situations. The 

 energy of the Weymouth pine is even greater in this 

 direction than that of the Scots pine, whilst that of the 

 black or Austrian and maritime pines is somewhat less. At 

 this stage of growth, unless the density of canopy be in- 

 terfered with by accidents due to climate, such as breakage 

 owing to accumulations of snow on the branches, or the 

 foliage be eaten up by swarms of caterpillars, or the bark 

 and sap-wood be destroyed by the larvae of Bostrichini, the 

 soil being well protected becomes greatly improved by the 

 rich fall of needles annually, which on decomposition form 

 good humus, and stimulate the soil to increased timber 

 production. The impetus thus given to the general energy 

 in growth favours, on the better classes of soil, the self- 

 assertion of the dominating and predominating poles 

 throughout the whole crop ; but on soils of the poorer 

 class the improvement thus brought about is apt to be 

 frittered away and dissipated in prolonging the struggle 

 between the dominating and the dominated classes, so 

 that what on one situation may be gained by close planting 

 in forcing up the poles and favouring the early development 

 of a distinctly dominating class, may lead to exactly the 

 opposite result on a poorer situation. Poles that have once 

 stood in shade seldom develop into good normal stems. . 



The age at which a natural interruption of the canopy 

 begins, and the rate at and extent to which it continues, 

 are matters varying in general according to the quality 

 of the soil, and the suitability of the situation for the 

 pine. On shallow soils, or those which, like lime or poor 

 sand, are easily heated, it begins to take place about the 



