178 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



growth layer and arc at 46.5 cm. overlap, so that where one is sharp 

 the other is diffuse radially from it. Because this is not true outward, 

 the sharp margin of one or the other must spiral outward. In 1939 

 the "outer thin" growth layer at 40 cm. expands on the long radius 

 into a thickness two and one-half times that of the inner growth layer 

 and acquires a diffuse lens which, within a relatively few microns (at 

 40- cm.), becomes sharp bordered. Branch XSC 13-2 possesses much 

 more uniformity throughout its length than does branch XSC 13-1. 



44 cm. 



1937 I see 



I dee 



1938 I see 



I sL 



I ms] 



1939 I see 



I sL 



1940 I sL 



1941 I see 



psg 



Table 127.—XSJJ i-i 



65 cm. 50 cm. 



1937 I see I see 



1938 I see I see 



I dee I dee 



ddw ddw 



1939 I see I see 



I sL I dL 



1940 inc inc inc 



XSC 13-3 (table 126) was frozen artificially at 33 cm. on June 14, 

 1941, and was cut off July 11, 1941. In the 1938 increment, the sharp 

 lenses at 44, 33, and 28 cm. and the sharp, complete, entire growth 

 layer at 42 cm. are connected with, and very probably induced by, the 

 1938 natural frost. In the 1939 increment at 33 cm., the two sharp 

 lenses are one compound lens. In the 1940 increment, the table seems 

 to indicate that here we have a case where a lens — a partial growth 

 layer — represents all the growth for an entire growing season. How- 

 ever, it is highly probable that the densewood encircles the sections. 



XSJf i-i (table 127) was frozen artificially at 50 cm. on May 10, 



