i; kin sir FOREST TREES 151 



dothe the lower portion of the bole ; the weakened energy 

 of the individual trees also predisposes them to attacks 

 from the larch moth (Coleophora laricella), and weakens 

 their power of resistance to infection from the cankerous 

 fungal disease (Peziza Wilkommii], which has followed 

 the larch from its Alpine home, and finds in the milder 

 climate of central and northern Germany, and throughout 

 Britain, more favourable circumstances for its develop- 

 ment than in the Alpine tracts where also it is indigenous 

 but can less frequently develop its spores. 



Such is the usual life-history of pure forests of larch 

 formed on inferior or merely average soils and situations, 

 and it is generally found advisable to utilise the crop about 

 the fortieth to fiftieth year, if the attacks of these two above- 

 named enemies have not necessitated clearance at little over 

 half that age. Without underplanting at an early age, pure 

 forests of larch can only be worked at any higher rotation 

 when the soil is of such exceptional quality that defective pro- 

 tection does not lead to marked deterioration. The more the 

 situation varies from the natural requirements of the larch, 

 the less is its cultivation in pure forests recommendable for 

 the production of good timber-stems ; where, however, a 

 preference has been given to rearing crops of larch in 

 this manner rather than as a subordinate in mixed forests 

 of other species, the formation of an undergrowth of some 

 soil-protecting species should invariably be undertaken by 

 sowing or planting at the time when the canopy begins to 

 he much interrupted, if it seems desirable to retain the 

 larch as standards for the production of largo timber in 

 place of gradually clearing off the crop, and utilising 

 the land for sonic other kind of timber. 



Mixed forests, in which the larch is the ruling species grow- 

 ing along with others of approximately similar age, should 

 not be formed, as any attempt at their formation could only 



