NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 1 55 



margin, thus giving us a comparatively rare case of both interior and 

 exterior lenses in the same annual increment. At 33 cm. the concur- 

 rent lenses are narrower and reduced in number from the sections at 

 43 cm. 



The branch was frozen artificially at 33 cm. on May 25, 1941, at 

 which time the increment was as wide as, or wider than, that for 

 1940. Apparently no growth occurred after May 25, at 33 or 23 cm., 

 that is outward on the branch from the portion frozen. At 43 and 

 33 cm. the cambium was almost wholly dead save for a cell here and 

 there containing protoplasm or a nucleus. In contrast, the cambium 

 at 23 cm. contained protoplasm nearly around the circuit. Although 

 not active, the cambium certainly was not dead. The growth layer 

 at 43 cm. either began to form earlier than it did farther outward, or 

 formed more rapidly, or went on to completion after freezing occurred 

 outward on the branch. The densewood at 43 cm. of 1941 was only 

 feebly lignified. 



Table 91. — TTP 24-2 

 47.5 cm. 42 cm. 



1937 I see I see 



I dee 



1938 I see I see 



1939 I see I see 



1940 I see I see 



I msec I psce 



1941 I dee 



inc inc inc inc 



It is probable that the increment labeled 1937 in TTP 24-2 (table 

 91) represents but the second half of 1937, the inner sharp, complete, 

 entire growth layer, not listed, being the first half. In 1940 the intra- 

 annuals become fainter outward. The branch was frozen artificially 

 on May 25, 1941. 



Although 1935 in TTP 24-3 (table 92) is designated "sharp, 

 complete, entire" at 35.5 cm., its growth layer was not as definite 

 as at 42 cm. The sections at 30 cm. came from the middle portion 

 of the branch length which was subjected to artificial freezing May 

 25, 1941. Sections at 35.5 cm. were cut in sequence outward from 

 that portion of the branch which lay within the rubber gaskets of 

 the freezing apparatus, the two columns of the table representing the 

 inner and the outer sections. The growth layer "diffuse, complete, 

 entire" of first 1936 at 30 cm. possesses as definite a contact as the 



