124 



PROPERTIES OF WOOD. 



10. Yield of the Chief Species. 



Regarding the yield per acre in solid cubic feet of the 

 principal species of North European trees, the following 

 statement has been compiled from data given by v. Baur, 

 v. Lovey, Kunzi, Schuberg, Schwappach and Weise. 

 Quarter-girth volumes are y^ths of those given, or approxi- 

 mately one quarter less*: 



These figures are for pure crops ; for mixed crops measure- 

 ments are not available, and averages taken from the above 

 figures will not give true results, as a soil that is of one 

 quality for any species may be of different quality for another 

 species, owing to their different requirements in soil, climate, 

 number of trees, etc. As regards the produce of thinnings, 

 figures are available for pure crops, but they are rapidly 

 losing their value, as new methods of thinning are coming 

 into vogue. 



E. DEFECTS IN WOOD. 



1. Defective Structure, 

 (a) Abnormal Tissi/cs. 



Abnormal parenchyma (callus) covering wounds, with 

 intermediate tissues eventually passing into ordinary wood, 

 may be termed occluding tissue. Whenever the bark of a 

 tree is crushed or removed by any injury such as beating it 

 to shake down fruit (chestnuts, etc.) ; cutting in it names or 

 figures ; abrasure by cart-wheels, falling trees, climbing-irons 



* For ;i derailed account of the yield of the different species of European 

 trees, cf. Schlioh's ' Manual of Forestry," vol. iii., " Forest Management, 11 

 :ird ed., 



