294 PRUNING. 



solar heat has the greatest influence. The sun, during 

 this season of the year, produces also a hardening in- 

 fluence upon the newly-inflicted wounds, which by 

 this means are sooner healed up, as the bark then 

 more quickly covers the wounds than if pruned at 

 any other season of the year. In order to test the 

 effect of so doing, we have pruned sycamore and birch 

 during December, and have found them bleeding from 

 the wounds during the succeeding April and May ; 

 but we have never found any injurious results from 

 pruning during summer and early autumn. At that 

 season of the year, when the sap-wood is maturing, 

 there is least danger of spray being produced from the 

 wounds, and equally little of the tree bleeding. 



Any pruning performed upon the branches of coni- 

 ferae should be done during September or October, as 

 during these months the fluids are in a more fixed 

 state, and are not disposed to ooze out so freely as 

 earlier in the season ; and if deferred till winter, the 

 wood being in an expanded state during frosty weather, 

 a greater portion of it would become decomposed before 

 the bark covers over the wound than if the operation 

 had been performed in autumn. As regards the prun- 

 ing of dead wood, the case is materially different, no 

 wound being thereby inflicted in the vital part of the 

 tree, and, consequently, the fluids remain undisturbed. 

 One reason, however, for pruning off dead wood in 

 spring and during summer, instead of during the colder 

 months of the year, is in consequence of the tendency 

 it has of lowering the temperature of the plantation : 

 dead wood probably produces that effect more com- 

 pletely than any moderate degree of thinning could do. 

 The benefit, however, arising from pruning off decayed 

 branches from pine and fir timber is so great, compared 



