114 COMPOSITION OF rOEEST CEOPS. 



generation is continually going on with more gr less vigour, and 

 success depends to a less degree on the forester's care and skill. 

 It does not, however, follow that in the new generation each spe- 

 cies is represented to an extent proprotionate to its relative value 

 or desirability. 



JC. In a mixed crop mistakes are generally less fatal in their con- 

 sequences and usually correct themselves, or are corrected by the 

 forester, more easily than in a pure crop, — =In the case of overfel- 

 ling or the excessive opening out of the leaf-canopy, the presence 

 of trees of various habits and requirements is the best guarantee 

 we can have for the early restoration of the leaf-canopy or forest, 

 as will be evident from the considerations developed under preced- 

 ing heads II, VII, VIII, and IX. The beneficial effect of this 

 on the soil is in every case real and unquestionable, but, as regards 

 the composition of the crop where nature is unaided, we have no 

 assurance that the canopy or forest will not be mainly reformed by 

 the less valuable and even undesirable species at the expense of 

 the more valuable ones, 



XI. Misoing species in a forest economises labour and time and 

 facilitates work and supervision. — -Given a certain definite area of 

 forest and certain species to be grown there. If these species are 

 raised pure, they will of course have to occupy as many distinct sec- 

 tions of the area ; so that if an annual supply of the wood of each 

 species were required, a portion of every section would have to be 

 worked each year, thus creating so many independent centres of 

 work. But if all these species were intermixed, the same result 

 would be obtained by working at only a single point each year, and 

 then the whole area need be divided only into a single series of coupes 

 of convenient extent, instead of into innumerable small patches 

 very difficult to look after and work, because those taken in hand 

 in any given year are necessarily scattered here and there, without 

 any definite order, all over the forest, 



XII. A mimture of species contributes in various ways towards 



equalising the length of the rotation required by our various species. ■ 



A species that protects the soil very imperfectly after a certain 

 comparatively early age has been reached, must, if growing pure, 

 allow it to deteriorate, unless the crop is at once cut and regenerat- 

 ed; otherwise the soil, deteriorating on account of the imperfect 

 leaf-canopy, must necessarily react on the species, and thus weaken 

 and arrest its growth, and induce premature decay. A soil-im- 

 proving species, on the other hand, even if growing pure, will never 



