NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. l6l 



Sections at 45.8 cm. came from the first tip flush of 1944 which was 

 approximately 20 cm. long ; sections at 28.7 cm. came from the second 

 tip flush of 1944 which was 2.8 cm. long. About one-third of the 

 way out in the 1944 increment at 45.8 cm. there occurs one of the 

 diffuse growth layers, whereas seven-eighths of the way out there is 

 a second one, undoubtedly corresponding to the second tip flush. The 

 inner growth layer records a variation of cambial and physiological 

 activity unrecorded in the tip growth. Since a wide-field binocular 

 revealed only three growth layers rather than the four actually pres- 

 ent, unstained sections under low power cannot yield an ecologic pic- 

 ture as complete as do stained sections under a microscope. The dif- 

 fuse, complete, entire growth layer in 1945 was made by a late spring 

 frost. 



Table 100. — WCh 3-1 



36 cm. p cm. TF 



1944 I see I see i 



I d are i gl 



WCh 3-1 (table 100) was cut from the tree January 21, 1945. The 

 extra growth layer at 9 cm. has an indefinite outer margin. Insofar 

 as relative position is concerned, the growth layer corresponds to the 

 arc at 36 cm. 



Table ioi. — XSC i-i 



81 cm. 68 cm. 



1932 2 see I see 



I psee 



1940 I see I see 



3 sL 



I s iL 



ddw 

 inc 



One of the sharp lenses is overlapping at 68 cm. in XSC i-i (table 

 ioi). The branch was frozen artificially April 8, 1940, and was 

 cut off May 10, 1940. The 1940 increment at 68 cm. is illustrated 

 in text figure 15, which shows a compound lens, an overlapping lens, 

 and a half -lens between the inner complete, entire growth layer and 

 the outer incomplete, entire growth layer. For the most part, the 

 incomplete growth layer in 1940 consists of frost-injured and re- 

 covery xylem. It is of moment to note the amount of xylem formed 

 not only before May 10 but also probably before April 8. 



