— 162 — 



tribution is the normal curve, and, therefore, in order to see how far the 

 skew curves diverge from the normal we must first observe how much /3i 

 and ^2 differ from zero and 3 respectively. Taking the i^^, column first, 

 we note that in all the cases ^J'^ is greater, but not more than 4 times, 

 greater than the probable error. Taking next the deviation of jSj from 3 

 in comparison with the probable error of ^.^ we see that except one case 

 ^2 differs from 3 by an insignificant amount. In one case the difference 

 is less than thrice the probable error and hence may be considered pos- 

 sibly or even perhaps, probably insignificant. 



Thus we get the general fact that the percentage distribution of 

 number of trees in diameter class of stand comes very close to the 

 condition demanding a curve of Pearson's Type I and sometimes a curve 

 of Type IV. 



The deviation of these frequency curves from the normal type I 

 believe to be due to an undue accumulation of individuals in the small 

 diameter classes. It seems, from our permanent sample plots for thinning 

 for Larix leptorepis and from data from Cryptomeria japonica and from 

 Chamaecy parts obtusa, possible that some of the individuals should to be 

 cut out by thinning. What the source of abnormality it is, of course, 

 impossible now to determine. Thus Schuberg and Guttenberg, the authori- 

 ties in German school, pointed out that the percentage frequency distri- 

 bution obeys the skew curve, while Prytz,^ the authority in Denmark, 

 stated that it obeys the normal curve. These consideration seems to be of 

 considerable importance as indicating the worth of diameter statistics 

 relating with the sort of thinnings. 



(b) On the development of height and volume of 



TEST trees in STAND. 



The corresponding development of height and volume of individual 

 tree in a given stand with that of the diameter at breast-height varies 

 with the age and the grade of thinning. On this point, Guttenberg wrote 

 briefly. The relation with respect to the corresponding development of 

 height and volume of test trees with that of diameter at breast-height 

 was at first investigated by Kopezky'-and discussed by Hadek and Carolyi.'" 

 Furthermore Gehrhardt^' published in his work " Die theoretische und 



