258 



Journal of Agricultural Research 



Vol. XX, No. 4 



These showed less than i > per cent of the plants with abundant hyper- 

 trophied lenticels and a total of less than 13 per cent showing any evi- 

 dence of hypertrophy. The results in the most heavily watered bed 

 and in the controls are given in Table I. The results with the pruned 

 trees shown in the table lead to the same conclusions as the results cited 

 above orj the unpruned trees namely, that heavy watering increased 

 the amount of lenticel hypertrophy. 



TABLE I. Effect of watering and top pruning on root-knticel hypertrophy of third-year 

 western yellow pine at Bessey Nursery, Halsey, Nebr., pruned in early July and examined 

 September 10 to 15 



Having 8 or more noticeably hypertrophied root lenticels per tree. 



b Including the needles that had appeared on the third-season shoot as well as those produced in earlier 

 years. Cut back to sheath but portion of needle remaining in the sheath left intact. 



PRUNING EXPERIMENTS 



Pruning experiments were conducted in an effort to throw a little more 

 light on the factors controlling the lenticel hypertrophy. The tops of a 

 number of rows of western yellow pine transplants at the Bessey Nursery 

 were pruned with different degrees of severity during the first week in 

 July, 1917. This is about the middle of the season of vigorous growth 

 at this nursery. The results of a root examination three months later 

 appear in Table I. The most heavily pruned plants showed the least 

 lenticel hypertrophy, with the exception of plot E in the normally watered 

 series. The percentage in this case is based on only 48 trees, only one- 

 third as many as furnished the basis for each of the other figures in the 

 three lower lines of the table. The pruning did not so injure the plants 

 as to prevent growth entirely, for even those most heavily pruned reacted 

 by sending out new shoots. 



