88 THE STHUGGLE FOE EIISTEITCB. 



than their rivals. Even should the forester be wanting in skill, 

 he is Hkely to make fewer mistakes in a crop of variously aged 

 individuals. 



(jf) Climbers. — There is no addition to make here to what has 

 already been said under the preceding Cases. Special attention 

 may, however, be drawn to the fact that the presence of dififerent 

 species and various ages necessarily implies the existence of several 

 stories of growth and, therefore, affords at all times every facility 

 for the ascension of climbers, although, on the other hand, tho 

 closer mass of roots in the soil and of foliage in the leaf-canopy 

 tends to keep them back during the first stage of their develop- 

 ment. 



IV. Density of the LfiAff-cANOPY, relative density and 



SHAPE OF CROWN, AND RELATIVE CAPABILITY OF PERSISTING UNDER, 



OR PUSHING HP THROUGH, COVER. — The shape, height, depth, width 

 and density of the crowns of trees and shrubs differ not only from 

 species to species, but according to their respective ages, also from 

 individual to individual belonging to one and the same species. 

 Thus it is in a mixed crop composed of individuals of all ages that 

 we find the greatest variety in these several respects. Two im- 

 portant results follow thence. In the fi,rst place, young individ- 

 uals of one species or another will generally be present and ready 

 to at once fill up any empty space occurring from whatsoever 

 cause in the leaf-canopy, and each and every species will be thus 

 given a fair chance of uiaintaining itself permanently in the crop ; 

 and, in the second pi 'soea crop of mixed species and ages will usu- 

 ally be the densest and most complete of all, 



V. Relative quantity and spread of the roots (includ- 

 ing THE rhizome). — Until decline sets in, the spread, closeness 

 and absorptive power of the roots of trees and shrubs increase 

 with age. Consequently young indi\'idual9, and particularly seed- 

 Hngs and saplings, are not only unable to push their roots about 

 in the soil, but may often be completely starved out, if they are 

 growing in the midst of, or under, a close growth of larger indi- 

 viduals possessing the same root-system. In the present Case, 

 however, owing to the variety of species present, there is alwavs a 

 chance of such stems having lor neighbours individuals possessing 

 a different root-system. They are thus enabled not only to persist, 

 but even to gradually establish themselves, until, an opening in the 

 leaf-canopy and more room in the soil, afforded by the disappearance 

 from time to time of some of their old or otherwise perishing 

 neighbours or by the contraction of the roots and crowns of those 



