CHAP, ix.] Tending of Woods 205 



the performance of the vital functions of the rest of the tree. 

 On the contrary, when the operation is carried out smoothly 

 and close to the stem, it prevents the formation of hard, horny 

 knots in the wood ; and this consequently enhances the value 

 of the timber, considerably diminishes the danger from fun- 

 goid diseases, and favours an early and complete cicatrization 

 of the wound-surface. It is therefore particularly to be recom- 

 mended in the case of Oak, Pine, Larch, Spruce, and Silver 

 Fir, whose dead branches are much more apt than in other 

 genera to form hard, tough snags, which, becoming gradually 

 embedded in the stem by the new growth of annual zones of 

 wood, diminish the value of the timber for technical purposes, 

 and thereby affect its market price. 



The removal of living branches is, however, a direct inter- 

 ference with the vital condition of the growing tree, and can 

 therefore only be ventured on to a limited extent. Under no 

 circumstances should more than one-third of the total quantity 

 of foliage be removed at one time ; practically, only about one- 

 fifth of the foliage is generally the extent removed during such 

 operations. Experience has shown l that, even in the case of 

 quick-growing kinds of trees, the removal of living branches 

 should ordinarily be confined to those that are not over 

 2\ inches in diameter for conifers, or not over 4 inches for 

 broad-leaved species of trees, as, otherwise, the process of cica- 

 trization cannot take place quickly enough to ensure hindrance 

 of the germination of fungoid spores producing disease. 



As the broad-leaved species of trees are not so liable as 

 conifers to fungous infection, they usually stand trimming 

 better. With reference to this matter Professor R. Hartig 

 remarks that 2 : 



When branches are removed from a tree, it thereby acquires a pre- 

 disposition for a number of wound-diseases, of an infectious or non- 



1 See Ney, Die Lehre vom Waldbau, 1885, p. 300; also Gayer, op. cit., 

 p. 584. 



a Lehrbuch der Baumkrankheiten, 1889, p. 15. 



