156 Studies in Forestry [CHAP. vn. 



to the reproduction of the crop (though not necessarily, so far 

 as the latter is concerned), but it is much more exposed to 

 climatic dangers like extensive windfall over areas covered with 

 Spruce, or to damage from snow and ice in Pine tracts, or to 

 attacks of insect enemies as with both Spruce and Pine, or 

 to cankerous fungoid diseases as in the case of Larch or Silver 

 Fir, &c. 



Pure forests cripple and confine the management to one kind 

 of timber practically in any one locality; and if the market for 

 that particular kind goes down and becomes unremunerative, 

 it is not easy all at once to pave the way for the production of 

 other and more profitable woodland crops. 



It will in general, therefore, be to the advantage of the land- 

 owner to avoid the formation of pure forests over extensive 

 areas. But occasionally it happens that there is little practical 

 choice about the matter. The land may be too poor for Oak, 

 Ash, Maple, Sycamore, Elm, Larch, &c. to grow in mixture 

 along with Beech, Hornbeam, Spruces, and Silver or Douglas 

 Firs, and then Pine forests are the best crops that can be formed 

 if the land is to be put under timber at all ; or undrainable 

 tracts may be better suited for Alders or Willows and Poplars 

 than for other genera ; or local requirements may be such that 

 a fairly well-assured and constant future market for one parti- 

 cular class of timber seems to point to its cultivation as most 

 advisable and attractive. 



In most mixed crops of about equal age certain species, 

 either through greater energy of growth in height, or in conse- 

 quence of soil and situation specially favouring their develop- 

 ment, or from a combination of both these factors, attain 

 advantages in rate and extent of development which induce 

 or necessitate a corresponding fall below the par of normal 

 development in the other species ; hence sooner or later these 

 latter species, unless specially tended, have to be removed 

 from the crop, even although they may not have attained their 

 physical and technical maturity. It thus happens that in many 



