NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 235 



The increments for 1939 and 1942 have 2 see each. 



TTC 33-13-a (1938-1942) 

 7 see + I dee + S sL + i dL — 5 years. 



Here, 12 sharply bounded growth layers represent five years. 

 Branch TTC 33-16 (table 166) was cut off July 31, 1944. 



Table 166. — TTC 33-16 



12.2 cm. 



1943 I see 



1944 2 msce 



jne 



Tip growth measurements on TTC 33-16 were made on January 

 30, 1943, January 22, 1944, and July 31, 1944; the sections were cut 

 from the tip growth of 1943. Hence, this branch is an example of 

 measured multiplicity. Note should be made of the amount of diam- 

 eter growth which had taken place before July 31, 1944. At 12.2 cm. 

 the cambium appeared to be active, whereas at 7.8 cm. it had become 

 inactive. 



The history and observation of branch TTC 33-20 (table 167) were 

 identical with those of TTC 33-16. 



Table 167. — TTC 33-20 



13.4 cm. 7.8 cm. 



1943 I see I see 



I d are 



1944 2 see 2 see 



inc ine 



The "inc" had practically completed its growth. The formation of 

 3 see by July 31 shows that the time of rapid xylem formation comes 

 during the first half of the warm season. 



TTC 34-2 0936-1941) 



a. 9 see + I msee + 2sL+ 3dL+id are + psg — 6 years. 



b. 6 see + 2 psee + 6 sL + i dL + i s 2L + psg — 5 years. 



Branch TTC 34-2 was dead at the time of cutting, November 29, 

 1941, its cambium having been killed by artificial freezing on May 18, 

 1 941. The presence of psg indicates that the cambium was active 

 when killed. To give an idea of the amount of growth that had oc- 



