SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 140, NO. 1, PLATE 1 



Fig. I. 



Fig. 2. 



Fig. I. TTC .,'j-70-/). Branch section of Ciiprcssiis arizonica, cut January i, 

 1943. Xylem of 1942 only. Densewood followed by postseasonal growth 

 whose cell columns extend variable distances into cambial region. Outer 

 margin of xylem is irregular and annual margin of growth layer would Iiave 

 been dififuse if growth had been permitted to continue. 



Fig. 2. TTC .?j-//-a. Branch section of Cnpressiis arisoiiica, cut Januray i, 

 1943. Xylem of 1940-1941. Multiple divided densewood in outer dw of 1940 

 annual increment. A first step in lens formation by a brief episode of cell 

 enlargement and perhaps a brief interval of variation in cambial activity. 



