110 COMPOSITION OF FOREST CHOPS. 



gravel and stones in concrete, so that it forms a closer-packed mass 

 of foliage than if the component crops were pure. Then again in 

 every forest, whether pure or mixed, the number of stems must 

 necessarily diminish progressively with advancing age by the death 

 and disappearance of some of the trees. Now in a pure forest, un- 

 less the component species be extremely shade-enduring, the inter- 

 vals thus produced between the similarly-shaped crowns of the 

 surviving individuals are bound to become wider and wider, until 

 at a comparatively early age the trees, all more or less of one and 

 the same height and habit of growth, stand well apart from one 

 another and cease to protect the soil except in a very incomplete 

 manner. In a mixed crop, on the other hand, during a consider- 

 able part of its life, the gaps produced by the disappearance of the 

 trees that succumb in the struggle for existence are at once filled 

 up by the upward or lateral extension of overtopped or adjacent 

 crowns, belonging chiefly to other species possessing a different ha- 

 bit of growth. Hence not only does the greater density of a mixed 

 forest become, as a rule, more conspicuous with increasing age, but 

 mixed crops generally maintain a complete leaf-canopy up to a 

 more advanced age than pure ones of the same species, an unques- 

 tionably great advantage for the forester in almost every instance. 



III. A judicious mixing of species increases the amount of ligneous 

 production. For the same reasons that the leaf-canopy becomes 

 denser in a mixed crop, and also because of the different root-systems 

 of the various component species, the number of stems standing per 

 unit of area at any age is larger than in a pure crop and the differ- 

 ence becomes more conspicuous with advancing age. Besides this, 

 the greater density of the leaf-canopy not only produces longer 

 boles and makes the forest grow up higher, but, by improving the 

 soil, it also prolongs the period of sound growth. All these cir- 

 cumstances result in a larger production of wood, and more parti- 

 cularly of timber. 



IV. It is only 1)y a 'mixture of species that with regular annual 

 working we can cultivate our more valuable species in the greatest 

 abundance ivithin any given area, over the widest extent of country 

 possible, and of the finest quality and size. Many of our most valu- 

 able species, like teak, Dalbergia latifolia, Lagerstrcemia Flos-Re- 

 3\>v &c., and, in many localities, even deodar and sal, grow natur- 

 uly in company with other trees. If we sought rigidly to obtain 

 pure crops, we should either have to clear away all these latter and 

 leave a few isolated individuals or patches of the former to form the 

 sum total of the standing growth ; or, if we also insisted on having a 



