NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 263 



trees WAp i and WCh 2 began a second tip flush during the week 

 prior to July 23. About five days prior to the initiation of tip growth, 

 the moderate crop of apples had been removed from WAp i. The 

 growth on WCh 2 indicates that this removal was not the inciting fac- 

 tor. The second tip flush on WAp i varied from i to 4 cm. in length 

 and had been completed between the 6th and 13th of August. At the 

 end of a period of high temperature, a rain of 6.2 inches fell on 

 August 2. The temperature remained low until August 11 when it 

 rose sharply to remain high until August 18. Between the 13th and the 

 20th, a few of the covered terminal buds on WAp i expanded and 

 burst open. Growth impulses had not yet ceased because on October 

 22, a 4-foot plum tree within 60 feet of WAp bore scattered blossoms 

 chiefly on branches from which the leaves had dropped. Late in No- 

 vember a newspaper carried a notice of the presence of cherry blos- 

 soms at the Tidal Basin in Washington. 



The main points of WAp i and WCh 2 history are paralleled by 

 WPe I except that in WPe i the second flush began immediately after 

 July 2;^ rather than just prior to that date, and except that growth con- 

 tinued until August 27. On the peach tree, the tips commonly with- 

 ered and died. One-third of the branches on WPe i grew second 

 flushes. 



Qualitative, with a slight admixture of quantitative, work is highly 

 suggestive as regards the effects of growth factors, but controlled ex- 

 perimental plots of trees would no doubt give us much more precise 

 information. Nonetheless, the observations of 1943 are perhaps 

 worthy of record. Trees and shrubs observed were apple, peach, red 

 cherry, black cherry, plum, oak, chestnut, dogwood, gooseberry, and 

 currant. Second flushes were present and common on all except the 

 one small cherry which was the last to leaf out in the spring. 



Weather notes were taken as follows: Winter 1942-1943, dry; 

 spring 1943, normal rainfall ; last three weeks of June, no rain, hot 

 with temperatures over 90° F. ; first two and a half weeks of July, 

 normal with periodic, but not too effective, rain ; rest of July, rainless ; 

 August 17, "0.17 inches rain last night, first effective rain since June 

 5" ; up to August 23, high temperature and no rain ; at the end of 

 August and the first of September, several good growing rains. In 

 the midst of the June dry period, the Japanese beetle attacked all trees 

 except the oaks. The attack tapered off the first part of July. Ten to 

 15 percent of the leaves were attacked except for one plum on which 

 90 percent of the leaves were affected. Each affected leaf was left 10 

 to 100 percent dead and brown by the beetles. They left only the 

 veins in the affected parts. With the exception of the plum tree which 



