264 COLLECTION OF STATISTICS. 



financial importance, such as a shelterwood (or nurses) over 

 another tender species, or a soil protection wood, standards 

 of valuable species, &c. 



The undergrowth, shrubs, herbs, &c., should also be 

 described. 



c. Density of the Growing Stock. 



To every method of treatment, as determined by the objects 

 of management, corresponds a normal densit}^ of the growing 

 stock. Deviations from that density are expressed by such 

 terms as over-crowded, under-crowded, open, very open, 

 interrupted, irregular, &c. Such terms are indefinite, and 

 subject to different interpretations. It is better to place the 

 normal density as equal to 1, and express the actual stocking 

 in decimals of 1. The degree of density can be determined by 

 ocular estimate, or more accurately by comparing the basal 

 area of the stems with that of a normally stocked wood, or still 

 more accurately by comparing the volume of the wood with that 

 of a fully stocked wood of the same age. 



When the density of stocking is insufficient, it should be 

 stated whether the wood is generally open, or whether the 

 deficiency is due to greater or smaller blanks. 



Under a blank is understood an area which, though it 

 belongs to the wood producing area, has no trees on it, or so 

 few that its complete re-stocking is necessary. Areas which are 

 not destined for the production of trees are not included here, 

 as they form part of the areas set aside for other purposes, 

 such as fields, meadows, &c., or are altogether unfit for the 

 production of trees, such as bare rocks, boulder drifts, swampy 

 ground which cannot be drained, &c. As regards the latter, it 

 is not always easy to draw the line between actual blanks and 

 woodland, as they frequently have a thin stocking, which may 

 give a small return from time to time. 



d. Age. 



The methods of determining the age of trees and woods 

 have been given at pp. 72 to 77. 



