NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 



193 



bright green, pliable, and "alive." They remained on the tree through- 

 out most of November but had fallen off completely by the 26th. 



The variety of tip behavior on a single tree is illustrated by the 

 observations of September 24 concerning WCh 2. Different branches 

 showed three different types of tip growth : 



1. Continuous growth all season. 



2. Early flush of growth, then setting of terminal bud; no further extension. 



3. Two tip flushes separated by terminal bud scale scars. 



There appears to have been no systematic distribution of the stages, 

 all three being noted on one large branch. However, the more primary 

 the branch, the more apt it was to have continuous growth throughout 



Fig. 43. — Plotted tip growth of Washington trees for 1944. 



the season (i, above), and the more secondary or remote the twigs, 

 the more apt they were to grow for a short time before setting a ter- 

 minal bud (2, above). Most instructive of all, no doubt, were the ter- 

 minal buds which broke out of their scales when the second flush be- 

 gan and then made no further growth. 



Branch WCh 2-2 is an example of continuous tip growth which be- 

 gan in mid-April and ceased between September 3 and 10. Weekly 

 measurements had been made from April 26 to November 26 ; near- 

 daily observations were made from the time of initial bud opening 

 until midwinter. Another branch, WCh 2-1, is also an example of 

 continuous growth, and its plotted measurements along with those of 

 WCh 2-2 are given on text figure 43. Even though WCh 2-1 had con- 

 tinuous tip growth during the 1944 season, two plateaus of decreased 

 growth rate are visible, one from about May 28 to June 25 and the 

 second from July 23 to August 13. The graph of WCh 2-2 shows 



