42 



foresters, each of the trees measured for analytical purposes is aualyzed 

 separately, aud for each individual tree a table of growth is prepared. 

 Then all the tables of growth are classified according to forest condi- 

 tions, ages, and degrees of dominance. Thereupon the tables assigned 

 to a group are averaged, and a table representing the rate of growth of 

 the group is thus obtained. Suppose, for instance, that 50 trees of a 

 given species were measured on a site under the same forest conditions 

 and then analyzed. Sux)pose further that the corresponding 50 tables 

 of growth, each of course representing the progressive development of 

 a single tree, havf> been divided into two distinct groups, according to 

 the accepted classification, one group containing 29 and the other 21. 

 Finding the average of the 29 tables and that of the 21 tables, the 50 

 analyzed trees would have been finally represented by 2 tables, each 

 representing the rate of growth of the corresponding group. 



These operations can be simplified by starting with the classification 

 of the trees when their measurements are taken in the forest, then 

 proceeding with the averaging of those measurements for each group 

 separately, and finally analyzing only the average tree of each group. 



The classification of trees can be performed in a more efficient and 

 accurate way in the forest than in the office. The measurements for 

 each group of trees can be taken separately and so arranged as to per- 

 mit the entering of sets of corresponding measurements of a homoge- 

 neous nature on separate sheets, thus facilitating their averaging. For 

 instance, all the measurements of cross sections taken at uniform heights 

 from ground would be entered on one sheet for all the trees of the same 

 group. By averaging, then, these homogeneous sets of measurements, 

 figures would be obtained representing the measurements of an average 

 tree of the group. The analysis of that average tree would determine 

 the progressive development of the group. Thus by reversing the 

 process of analysis the rate of growth of the 50 trees taken in our exam- 

 ple could be determined by the analysis of only 2 trees, each being an 

 average for one of the two corresponding groups. 



While the work in the field and the averaging either of the tables of 

 growth or the sets of homogeneous measurements will consume the 

 same amount of time, the time required for the analysis itself of the 

 50 trees would differ in the two cases in the proportion of 2 to 50, i. e., 

 the modified method would have required only one twenty-fifth of the 

 time that would have been consumed by the analytical method as prac- 

 ticed by European foresters. The saving of time will be more appre- 

 ciated when it is known tkat the complete analysis of a single tree of 

 seven to nine cross sections, including the preparation of the table of 

 growth, takes a day's work. Determination of the rate of growth of 

 the 50 trees would consume 50 working days, while under the present 

 arrangement 2 days are sufficient to arrive at the same results. 



The detailed discussion of the method, accompanied by an actual 

 example, will enable the reader to understand its working more clearly. 



