oZ jOL'KXAI, ol- l-iiUI'.STin- 



niiif^s. 'I1u' (lata recorded show a striking increase in the width of the 

 annual rings soon after the thinnings were made. He C(jncludes that 

 "the width of the annual rings diminishes toward the top (of the 

 trunk), although the increase in growth in comparison with the earher 

 develo])nient is there also very great," and states further that the reason 

 for the added increment heing deposited in the lower trunk is not very 

 clear. 



The present studies have shown both for hemlock and grand fir that 

 the thinnings very marked!}' affected the diameter growth, the total 

 height, and the size of crowns, producing in the case of grand fir a dis- 

 tinct and separate secondary crown. The data are to be accepted as 

 evidence that through thinning the trees have recovered from suppres- 

 sion to a remarkable extent and have passed from a low to a high vigor 

 status. The increased vigor has been made evident through greater 

 increment. In co-ordination with these physiological activities the 

 crowns have developed to as much as twice their former size in the 

 case of the hemlock and produced secondary crowns equal to and at 

 times surpassing the original crowns in the case of grand fir. Such 

 activity and renewal of vigor cannot help but possess beneficial effects 

 in respect to the development of the tree and, it appears, must also play 

 an important part in checking the number of sporophores produced on 

 the trees. 



In order to determine the possible eft'ects of thinning upon the two 

 tree species studied, the data for both hemlock and grand fir in Tables 

 I and 2 respectively w^ere reduced or increased according to the signs 

 indicated in each column and to the percentage indicated. This was 

 done to allow for the original differences between the two stands prior 

 to cutting operations and was based upon the differences between the 

 mean annual diameter growths of the trees on the two areas. In hem- 

 lock the mean annual diameter growth on the cut-over area was found 

 to be 143 per cent greater than a similar figure on the uncut area and, 

 v-ice versa, 41 per cent less. Thus, as an example, by reducing 11 

 inches, the average diameter breast height for the cut-over area, by 41 

 per cent gives 6.5 inches as the average diameter (breast high) for the 

 cut-over area after reduction. This comes within 0.45 inch of the aver- 

 age diameter (breast high) given fc^ir the imcut area. Tn the continua- 

 tion of this process the number of live sporophores was increased by 

 143 per cent, as was the total number of infected trees and the total 

 number of trees bearing sporophores. The +143 per cent and — 41 

 per cent were applied according to whether the reduction of the original 



