NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. II9 



bium on the short radius became active. The extreme variation of 

 cambial activity in a decided lower forest-border situation not only 

 among different trees but among branches of the same tree also comes 

 into relief by contrasting the thick growth layers of 30 or more cells 

 with the situation noted in TTP 24-3-a and kindred sections (pis. 17, 

 fig. i; 19, fig. i). There a growth layer, represented elsewhere in 

 radial thickness by many cells, is made up of one densewood cell over 

 a portion of the circuit and by very few more over the remainder. 



Cambial activity may be related to the absolute vitality of the cam- 

 bial initials. This may be illustrated by several branches of TTP 20, 

 a tree probably of less than average vigor. 



Table 45-— TTP 20-1 



37 cm. 5 cm. 



1939 I see I see 



I dL 



psg 



Branch was cut oflf November 26, 1939. 



At 37 cm. in TTP 20-1 (table 45), the condition of the cambium 

 was variable ; some cells were alive, some plasmolyzed, the rest dead. 

 At 5 cm. most of the cambium was alive. 



Table 46.— TTP 20-2 



44 cm. 24 cm. 12 cm. Bud 



1939 I see I see i see i inc 



I dL I psee i ee (narrow cells 



(faint) in patches) 



Branch was cut oflf December 14, 1939. 



The outer cells of the xylem in TTP 20-2 (table 46) were imma- 

 ture. At 44 cm. cambial cells were in part nucleated, in part plas- 

 molyzed ; at 24 cm. the cambium was in good condition ; at 12 cm. 

 and at the bud it was excellent. 



Table 47.— TTP 20-3 

 18 cm. II cm. Bud 



1939 I concurrent L i cone. L i psce 



(part immature) 



Branch was cut oflf December 15, 1939. 



At 18 cm. in TTP 20-3 (table 47), the cambium was mostly alive, 

 some cells plasmolyzed ; at 1 1 cm. and at the bud the cambium was in 

 cfood condition. 



