TENDING OF CROWDED WOODS. 203 



closed as quickly as possible and made impermeable to 

 tho spores of fungi and to water. This is effected by 

 nature through the process of occlusion, provided the 

 wound does not exceed a certain size. The time 

 required for this operation depends on the size of the 

 wound, the vigour of the tree, the manner in which the 

 wound is made, and above all, on the species. 



Pruning green branches is least dangerous and objec- 

 tionable in the case of Oak and Conifers which are in 

 vigorous health, provided the operation is carefully done 

 and the wound does not exceed 3 inches in diameter. 

 Oak closes the wound rapidly by occlusion, while wounds 

 on Conifers exude turpentine, which protects them to a 

 considerable extent. 



As regards other European species the evidence is 

 at present conflicting. Pruning green branches of 

 Poplars, Birch and Willows is undesirable, because 

 their wood is liable to rot quickly. According to 

 Hess some of the important species may be arranged 

 in the following descending series in respect of 

 the activity of occlusion : Broad-leaved species : Oak, 

 Beech, Hornbeam, Lime, Ash, Maple, Birch. Conifers : 

 Larch, Silver Fir, Scotch Pine, Spruce. 



Under any circumstances the pruning of green branches 

 should not be undertaken without due consideration of 

 the advantages which are likely to be realized and the 

 disadvantages connected _with the operation ; this is of 

 special importance in all cases where the objects of man- 

 agement centre in the production of large- sized timber, 

 which can only be obtained by permitting the trees to 

 grow and increase for many years after the pruning has 

 been carried out. 



