TENDING OF CROWDED WOODS. 199 



A. Removal of dead, injured or otherwise undesir- 

 able trees. 

 13. Pruning. 

 C. Thinning. 



A. Removal of Dead, Injured, or otherwise Undesirable 



Trees. 



Iii every wood single trees or groups of trees sicken 

 or die from a variety of causey. Amongst these may be 

 mentioned an unfavourable soil, frost, drought, fire, hail, 

 lightning, injuries to the crown, stem or roots, attacks by 

 insects or parasitic fungi. Again, the crowns and stems 

 of trees may be broken by strong winds, snow and rime, 

 or single trees and whole groups may be thrown down. 

 From one or the other of these causes, there will 

 always be found a certain quantity of material which, if 

 not removed as speedily as possible, will stimulate the 

 increase of injurious insects and of fungi. The latter 

 have of late years been recognized as the cause of 

 considerable damage to woods, since modern botanists 

 have explained many important phenomena formerly 

 imperfectly understood as to their origin. In this 

 respect attention is invited to the ravages of Trametes 

 radicipcrda and Agaricus melleus in Scotch Pine and 

 Spruce woods ; of Trametes Pini, Peridermium Pini in 

 Scotch Pine woods (so-called foxy trees) ; Peziza Will- 

 /commit, the Larch cancer fungus ; JEcidiiim elatinum, the 

 Silver Fir cancer fungus, the various species of Polyporus 

 on broad-leaved and coniferous trees, &c. 



Far greater, however, than the danger from fungi, is that 

 from insects. Many species of the latter are apt to become 

 disastrous to whole woods, extending over large areas. 



