152 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



because of its relations to the increment for 1940. Perhaps it is 

 worthwhile to emphasize at this point that under low powers and 

 with an absence of absolute dating, the outer border of the first growth 

 layer of 1939 would be considered an annual border and the true 

 annual margin of 1939 would be identified as an obvious "double" of 

 the next outer growth layer. Under low power the 1940 increment, 

 both at 48 and 22 cm., appears to be a series of concurrent lenses. 

 Under high power it appears to be continuous around the circuit, 

 dwindling, however, to a thickness of one or two rows of narrow cells 

 which lie against the densewood of 1939 and are indistinguishable ex- 

 cept by continuous tracing under high power. Lightwood is lenticular 

 in truth, but densewood, and therefore the growth layer, is continu- 

 ous around the circuit ; at no point did the cambium fail to divide. 



Table S7.—TTP 22-1 



5.8 cm. 3.8 cm. TF 



1940 I see I see I 



1941 I see I see I 



I dee I dee 



TTP 22-1 (table 87) was cut from the tree January 17, 1942. Dat- 

 ing is certain because of tip-growth measurements. Sections at 5.8 cm. 

 came from the 1940 tip flush, whereas those at 3.8 cm. came from the 

 1941 tip flush. 



Apparently there is an anomolous situation as set out in the above 

 chart — a 1940 increment out in the tip growth of 1941. Because of 

 tip measurements and because of the striking similarity between the 

 sections from 5.8 and 3.8 cm., the dating of the growth layers is con- 

 sidered to be accurate. Sections at 3.8 cm. were cut from the meas- 

 ured tip flush of 1941, it is true, but from within the longitudinal 

 reach of the measured length of the terminal bud (3.2 cm.) as it 

 existed prior to the start of 1941 growth. In other words, if we are 

 correct, a substantial amount of "1941" growth actually was formed 

 in 1940. A growth layer of a previous year is thus found within the 

 reach of the succeeding year's tip growth. 



What age should be assigned to the "1940" growth layer included 

 in the 1941 tip flush? Was "1940" actually present in the terminal 

 bud before 1941 growth began? If so, was xylem of "1940" mature 

 before 1941 ? What are the ecologic implications? 



This phenomenon is considered later, on pages 199 and following. 



