264 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I4O 



was 90 percent afifected, the relatively small amount of beetle damage 

 did not seem adequate to cause a second flush. Furthermore, the same 

 branches were not affected, and the damaged leaves were not replaced 

 by new photosynthetic surfaces. 



The record of second tip flushes and leaf drop was sketched during 

 the summer. By July 26, the length of the second flush on the various 

 trees varied from 2 to 15 cm. on first flushes of 5 to 30 cm. or more. 

 Two plum trees growing side by side showed, in the one case, distinct 

 terminal bud scale scars between the two flushes of 1943, whereas in 

 the second case, no terminal bud scale scars existed between the two 

 tip flushes. Growth continued at least until July 31. The second flush 

 on the branches of a 12-foot-high oak varied from 13 to 15 cm. to 

 which no further growth was added during the following nine days. 

 By August 8 native, as well as planted, trees had begun to shed their 

 leaves. A large mulberry, near the fruit trees, and gooseberry bushes 

 were losing their leaves. Currant bushes had lost from 50 to 100 per- 

 cent of their leaves. The second flush on a black cherry tree had 

 grown 15 to 20 cm. beyond the midseason terminal bud scale scars. 

 Several shoots on a gooseberry bush had grown a second flush of 9 cm. 

 whereas the remainder of the shoots on the bush appeared not to have 

 grown any during the season. In the 10 days subsequent to August 8, 

 leaves continued to drop. Now the leaves on dogwood and oak were 

 also dying. Some of the gooseberry and currant bushes had lost all 

 their leaves. They were falling from native large-leaved trees in the 

 woods. Spots of grass in lawns began to die, but this occurred defi- 

 nitely after trees had begun to lose their leaves. 



It seems quite clear, not only from the present work but also from 

 that of other students, that the cambial activity wave is complex in 

 nature, has a variable amplitude, and may have a length far shorter 

 than a year. The abundance of intra-annual lenses and the less com- 

 mon intra-annual, sharp, complete, entire growth layers testify to sec- 

 ondary activity waves in the cambium, whereas minor growth layers 

 such as arcs, interrupted lightwood or densewood, and divided dense- 

 wood or lightwood indicate minor fluctuations superimposed on the 

 larger waves. One wishes that there were always one sharply de- 

 lineated major wave a year with superimposed waves always revealing 

 themselves somewhere within the crown or trunk of the tree. Without 

 complete dissection of the tree, some of the revealing spots will be un- 

 detected, and the magnitude of the factor of multiplicity will be un- 

 known. 



Another matter impinges directly upon waves of cambial activity. 

 One or two students have held that drought can so reduce cambial ac- 



