278 KNUDSON: CAMBIUM DEVELOPMENT IN AMERICAN LARCH 



to June 3 the growth was markedly increased, while from June 3 

 to June 15 seemingly little growth occurred. After June 3 it 

 appears that relatively few new phloem cells were formed, but 

 growth consisted more of an enlargement of the cells already 

 formed. Some of the figures for June 15 are less than the corres- 

 ponding figures for June 3. This may be perhaps explained by 

 the fact that the cuttings were made somewhat lower, or better 

 perhaps by the fact that in obtaining these cuttings they were not 

 taken on a line directly below the preceding, but to one side. 

 Mer (loc. cit.) draws special attention to the well-known obser- 

 vation that wood growth is not always uniform on all sides of the 

 tree. 



Cutting. 



DIAGRAM i. Diameter of cambium and new phloem at various different dates. 

 A, Nov. 13; B, April 19; C, May 25; D, June 3. 



