150 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



end of 1942 tip growth; those at 24.3 cm. from middle of first 1943 

 tip growth which was 1.4 cm. long; those at 17 cm. from middle of 

 second 1943 tip growth which was 13.3 cm. long ; and those at 5.2 cm. 

 from middle of 1944 tip growth. At 24.3 cm. each tip flush of 1943 

 has a corresponding diameter flush. The diffuse growth layers of 

 1944 have their densewood buried in compression wood; that is to 

 say, the diffuse lenses at 26 cm. are actually composed of compression 

 wood some of whose cells are sufficiently narrow and continuously 

 oriented to give densewood. At 17 cm., a complete circuit of compres- 

 sion wood contains an arc of narrow cells — hence the designation of 

 one diffuse arc. At 5.2 cm., lenses and arcs of compression wood are 

 present but contain no narrow cells, no hint of intra-annual dense- 

 wood. Sections at 26 cm. show that simplification occurs inward on 

 the branch. 



Table S5.—TTP 21-7 

 41 cm. 24 cm. TF 



1938 I msce I psce i 



1939 I see I psce i 



I dee I dee (faint) 



1940 2 see I see I 



I dee 



The branch, TTP 21-7 (table 85), was cut from the tree Novem- 

 ber 9, 1940. In 1938, the outer margin of the increment becomes 

 somewhat more indefinite outward on the branch. 



At 41 cm. in 1939, the outer growth layer is much thinner than 

 the inner growth layer ; in fact, on the short radius, the densewood of 

 the inner growth layer makes contact with the densewood of the 

 outer growth layer. This local absence of lightwood forces the outer 

 growth layer to assume the appearance of a lens which, of course, it 

 is not. The lightwood is lenticular, to be sure, but not so the dense- 

 wood. A magnification of low amount would be powerless to resolve 

 the 1939 growth layer. At 24 cm., the one diffuse, complete, entire 

 growth layer of 1939 has disappeared except for very slight traces. 



The outer growth layer of 1940 at 41 cm. possesses lenticular light- 

 wood, but entire densewood, in much the same fashion as 1939 does. 

 Over a short arc the densewood is made up of one to two cells 

 radially. At 24 cm., the inner growth layer of 1940 has lost its definite- 

 ness — it has faded and diffused. 



The branch, TTP 21-8 (table 86), was cut from the tree Febru- 

 ary I, 1941. At 48 cm. the relation of compression wood to dense- 



