634 Forestry Quarterly. 



the lower classes, however, not even with the small per cent, 

 which they form of the total volume." 



The remarkable fact is that in a lo-year increment period 

 more than half the stems changed their position in class. If a 

 stem in one period of five years did not keep its place in relation 

 to the increment increase of all other stems, i. e. lapsed, it would 

 still further lapse in the next period. The same tendency in the 

 opposite direction was observed for stems which got ahead. 



The middle stem classes showed the greatest variation in growth 

 energy, while the stoutest and the slimmest trees showed the least 

 or altogether no change in position in these five- and ten-year 

 growth periods. The change in relative growth energy of the 

 single trees of a stand appears much greater than has been usually 

 assumed. 



As regards the stem classes according to Kraft's prescription 

 they show more sharply these changes and contrasts. 



The author points out that in the practice of thinnings the Kraft 

 tree class differentiation is the best one by which to determine 

 the laggards to be removed and the vigorous growers to be fa- 

 vored. 



Ueber das JVachstum dcr Kraftschen Stammklassen im Verlauf einer 

 sehnjahrigcn Ztizvachsperiode. Zeitschrift fiir Forst-und Jagdwesen. 

 September, 191 1. Pp. 663-686. 



In a very thoughtful article, Eberbach 

 Relations proves mathematically that the money rate 



between per cent, at which a management class under 



Volume sustained yield works is always less than the 



and volume increment per cent. The latter, 



Value however, gives an approximate idea of the 



Production. money interest (p) attainable, which as a 



rule, remains 20 to 30% under the volume 

 interest (q). Therefore, to improve p, one must improve q, which 

 can only be done by either raising the felling budget or reducing 

 the stock capital, and as the latter alternative rarely recom- 

 mends itself, all effort must be made to increase the increment, 

 which can be mainly done by a proper thinning practice, generally 

 speaking by taking out the trees which do not grow at a profitable 

 rate and leaving those which do, no matter how old or stout they 



