NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 1 77 



contains only one narrow densewood cell radially. Multiplicity in 

 1938 decreases outward, whereas in 1940 it increases outward. 



The impact of artificial freezing on the formation of xylem em- 

 phasizes the variations brought about by different conditions in dif- 

 ferent years, on different sections, and even on different branches. Ex- 

 Table 124. — XSC 13-1 

 50.5 cm. 38 cm. 27 cm. 



1938 3 msce 2 see i see 



I psce 

 I sL 

 ddw 



1939 3 see 3 see 3 see 



I dee I dee 



I msL I msL 



ddw 



1940 I see I see i see 



I msL I msL 



I dL I dL 

 ddw ddw 



1941 inc inc ine 



Table 125. — XSC 13-2 



46.5 cm. 40 cm. 40 — cm. 34 cm. 27 cm. 



1938 I see I see i see i see i see 



I msec I msce i psce i dee i dee 



I dL I dL I dL I dL 



I s arc I s arc i s arc i d are i d arc 



1939 2 see 2 see 2 see 2 see 2 see 



I sL I sL 2 sL 2 sL 2 sL 



I dL 2 dL I dL I dL i dL 



1940 I see I see i see i see i see 



I s iL I s iL I s ^L I s iL I s iL 



I d ^L I d ^L I d iL I d iL i d iL 



1941 I pee I ce i pee i pee i pee 



psg psg psg psg psg 



tensive application of artificial freezing would no doubt yield much 

 information on the exact time of xylem deposition under various 

 conditions. 



XSC 13-2 (table 125) was frozen artificially at 34 cm. on June 14, 

 1941, and was cut of June 27, 1941. In the 1938 increment, all intra- 

 annuals become weaker and progressively more diffuse outward on the 

 branch. The sharp portions of the mostly sharp, complete, entire 



