86 REPORT OF THE FOREST, FISH AND GAME COMMISSION. 



felled for each group. Experience has shown that correctness of result with an 

 insufficient number of sample trees cannot be expected. Less than two for each 

 group is sufficient only exceptionally. It is better to take from three to five, and in 

 poor stands even more. 



Deviations can be made here also from the reckoned diameter in choosing the 

 sample trees. They may even be chosen freely from the groups, if only the sum of 

 the basal areas approximates closely that of the calculated sum. 



The objection is raised against the Draudt and Urich methods, that as the sam- 

 ple trees are chosen in proportion to the number of trees and not in proportion to 

 volume, the groups containing the smaller trees have more than their proper share. 

 Moreover, in those groups a deviation in choice of sample tree is more noticeable. 

 These objections can be overcome by choosing so many trees that in any case, even 

 in the strongest groups, the required accuracy is reached. 



The Hartig Method. 



Hartig presents another way. He forms groups of the same basal area, and for 

 each of these groups the same number of sample trees is chosen. 



By dividing the sum of the cross areas of the stand by the number of groups to 

 be formed the cross area of each group is obtained. The trees are then grouped 

 to give this area, which, when divided by the number of trees in the group, gives 

 the cross area of the sample tree. 



By this method the sample wood cannot be worked up in one lot, but the 

 volumes of the individual groups must be reckoned. For this reason, and on 

 account of the somewhat complicated calculation in forming the groups the method 

 has been but little used in practice, although it is more accurate than the Draudt or 

 the Urich method. It is especially useful in scientific investigations and in stands 

 with only a few trees. 



Tabular demonstrations of the Urich and the Hartig methods have been 

 omitted for lack of space. 



