i»8(i JOURNAL OF FORESTRY 



normal trees it will not require many trees to determine the form 

 quotient which in any stand will be found to vary within probably 

 less than one to four per cent. (2) The simplest, even if not the 

 most accurate way of determining the form quotient is obtained indi- 

 rectly from the "form point method." The form point is the center 

 of gravity of the crown as seen from the side. That is. the center 

 of gravity of a vertical section through the center of the crown of 

 the tree. This point is located and expressed in figures by giving 

 its relative location in per cent of the total height of the tree. It 

 is determined thus: If one considers the crown of a normal tree 

 one can readily determine approximately where the center of gravity 

 of the crown seems to be. For instance, if the crown were triangular 

 this point would lie about one-third of the way up the crown ; if the 

 crown were square it would be in the middle of the crown. Taking a 

 fractional hypsometer or any rule graduated in ten parts, one holds it 

 vertically, extending the arm in such a way as to line in the top of 

 the tree under observations on the ten mark and simultaneously line 

 in the stump on the zero mark. Glancing quickly at the spot, where 

 one had decided the form point w^as located, one notices where it 

 seems to line in on the scale. As the scale is in ten parts, the reading 

 at this point indicates the per cent of the tree's height at which the 

 form point is located. The form point is now used as argument in a 

 set of Jonson's tables giving the relation between form point and 

 form quotient. 



Each per cent is considered as a unit of form point relative height. 

 Generally speaking, the form point is situated at 50 to 75 per cent of 

 the height for ordinary trees. Two form point units' variation causes 

 less than one unit variation in form class, thus it can be seen that the 

 volume figures are not greatly affected and that a good average can 

 be secured with a relatively small number of readings. In any stand 

 the average run of form points found should be within ten units, that 

 is, for instance, between 0.60 and 0.70. (Spruce and fir will generally 

 have a form class around 0.65, pine in dense stands may have a form 

 class of over 0.70.) 



One should not apply the form point to individual trees ; this needs 

 no comment, for all figures and tables used in forestry work are made 

 up from, or deal with, averages. The form point is not an exception 

 to this rule. Used with discretion it will give results which will 

 always lie within the accuracy required for practical purposes. For 



