2 5 8 



Journal of Agricultural Research 



Vol. XX, No. a 



These showed less than iK 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 on the unpruned trees — namely, that heavy watering increased 

 the amount of lenticel hypertrophy. 



Table I. — Effect of watering and top pruning on root-lenticel hypertrophy of third-year 

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

 September 10 to 15 



Plot. 



ABC 

 DE 



Part removed by pruning. 



All the secondary needles b 



All the secondary needles b and 

 tip of third season terminal shoot. 



All the secondary needles & and 

 entire third-season shoot 



Third season terminal shoot only 



Half the secondary needles only b 



Unpruned 



Additional unpruned rows scat- 

 tered among the different series. 



Heavily pruned. 

 Lightly pruned . 

 Unpruned 



Number of 



trees 

 examined. 



Heav- Nor- Heav 



ily mally ily 



watered watered watered 



series, series, series. 



Percentage of 



trees with 

 hypertrophy. 



185 

 182 



32 

 108 



58 

 206 



49 



399 

 166 



255 



42 

 47 



Si 



48 



o 



72 



7i 



140 



143 



Nor- Heav- Nor- 

 mally ily I mally 

 watered watered watered 

 series, series, series. 



6 



41 

 3i 

 58 



5i 



9 



37 



57 



Percentage of 



trees with 

 strong hyper- 

 trophy. 



17 



C3 



2.9 



17 



19 

 17 

 33 



24 



2-3 



18 

 3i 



1.4 



a Having 8 or more noticeably hvpertrophied 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 w.ere 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, 1 91 7. 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. 



