SHAPE OF TREES, ETC. 



Mayr gives the following data : 



Breadth of Sapwood in 



Centimeters. 



Up t.) 15 



:? :, 



510 

 Over lo 



Yew, larch. oak. 



Scuts [lino. Weyutoiith pine, spruce, silver-tir, 

 .Maples, dins, ash, walnut. 

 Other broadleaved ' : 



As already stated, sweet-chestnut, laburnum, robinia and 

 mulberry may be added to the first class of trees with narrow 

 sapwood. 



Freedom from branches, or cleanness of bole, is one of 

 the most important properties of economic timber. All 

 superincumbent boughs and foliage shade the lower and 

 earlier formed branches and causes their death sooner or 

 later, according to their greater or less susceptibility to shade. 

 This natural clearance of the lower branches and foliage is 

 effective in trees in an open position only partially and up 

 to a certain height. Whenever not only the crown of the 

 individual tree, but also the branches of neighbouring trees 

 unite in giving shade, as is the case in a dense crop, the lower 

 1 tranches of shaded stems must die rapidly, so that, by a proper 

 density of crop, a forester can readily obtain boles that are 

 clean up to a desirable height. Whenever, by a thinning, a dense 

 crop receives more light the death of lateral branches ceases. 



It is therefore evident that the early crowding of a crop is 

 desirable, and all factors that retard this, such as wide 

 planting, are prejudicial to the quality of the produce. 

 Attempts to remedy this by pruning are in the first place 

 costly and the resulting produce is saleable only near large 

 towns, whilst it is dangerous to the health of the trees. 

 Pruning is useful as long as only dead branches are removed, 

 but when living branches, especially over 2 3 inches in 

 diameter, are pruned away, either callus growth covers the 

 wound and at't'ects [lie, quality of the wood injuriously, or 

 fungi and insects attack the wounds, while desiccation by the 

 sun and moisture from the air increase the damage greatly. 

 In broadleaved woods epicormic shoots that require fresh 

 pruning may spring from the edges of the wounds. 



