lo Forestry Quarterly. 



aptly expresses the idea of a quotient which is an index to the 

 form of the bole of the tree I have adopted it, and for short we 

 shall call it q-^ to distinguish it from q-^ or ^3 which would 



represent the form quotient obtained bj' using the diameter at )% 

 or Yx height, respectively, as the upper diameter. 



The form factor and the form quotient of any tree being mutu- 

 ally dependent for their magnitude on the shape of the bole of 

 that tree, it follows that they must bear a very close relation to 

 each other. Schiffel found that this relationship varied some- 

 what with varying heights of the trees but that in stands of com- 

 paratively even height, such as mature stands, the variation was 

 very slight and when the / and the q^ were expressed in per 



cents, the difference averaged about 21 which we may term a 

 constant (C) for that species. This constant, it will be noted, is not 

 appreciably affected by variations in the form of the stem due to 

 age, site, or silvicultural conditions, the form factor and the form 

 quotient being both similarly influenced by such variations. 



This then gives us the simplest method that has yet been sug- 

 gested for the determination of the approximate form factor of a 

 tree, viz., divide the breast-high diameter into the diameter at 

 middle height, multiply by 100 and substract the constant, or to 

 express it as a formula, 



( ^ >< ^°° ) - ^ = / 

 The accuracy of the result will vary from tree to tree, but the 

 maximum variation in any coniferous tree that would be nearly- 

 enough normal in development to be selected for a sample tree in 

 measuring a stand would not exceed 6 per cent. Where a num- 

 ber of sample trees are taken, the error would be compensating 

 and could be wholly neglected, provided the c had been carefully 

 determined for the species. 



That the constant should vary in different species was to be 

 anticipated. Unfortunately very little exact work has yet been 

 done in testing this point in different species. What has been done, 

 however, seems to indicate that the variation may after all be con- 

 fined to relatively narrow limits. The Scotch Pine has been found 

 to give a C of about 20, while that of the European beech is be- 

 tween 22 and 23.' The similarity in value of the constant here 

 between the species varying so widely in habit of .stem growth. 



