NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 247 



In XSP 2-2, I see corresponds to each of the years involved. But, 

 in this otherwise simple sequence, one sharp lens intrudes to give a 

 single touch of multiplicity. 



Table 173.— XSP 2-3 



44 cm. 



1936 I see 



ddw 



1937 I see 



1938 2 see 



1939 2 see 



1940 I sL 



inc 



In a third branch of the same tree, XSP 2-3 (table 173), multi- 

 plicity again increases so that it summarizes as : 

 6 see + I sL 4- ddw + inc — ^4 -}- years. 



The branch was cut off June 12, 1940, by which time concurrent lenses 

 and an almost complete, entire growth layer had been formed. 



YCt 1-3 (1940) 



a. 4 see — I tf — I year. 



b. 3 see -f I sL — I tf — I year. 



YCt i-6-a (1940) 

 3 see — 2 tfs — I' year. 



The branches designated YCt i came from the tip flush which grew 

 during 1940, but not necessarily from the same tree. Definite evidence 

 of growth cessation was absent although the sections were cut No- 

 vember 21, 1940. In fact, a majority of the sections were growing at 

 the time they were cut. 



YCt 2-i-a (1939-1940) 

 IS to 20 gls — 2 or 2* tfs — 2 years. 



YCt 2 includes all branches containing the growth of two years, not 

 necessarily from the same tree. The sections 2-1-a gave a bit of 

 trouble because of the rapid succession of zones of vessels and zones 

 of narrow, much lignified tracheids. Clearly evident were the growth 

 pulsations. Up to 20 entire growth layers and lenses are present in 

 sections a. In b, the growth layers are fewer in number and more 



