Plate 31 



Fig. I. XSC ii-3-l>. Branch section of Cuprcssns arizonica, cut September 2"/, 

 1941. Xylem of 1938-1941. Striking "outer thin" gl of 1939 and evidence of 

 its age by position of 1940 frost effects ; weak and thin dw of "outer thin" gl 

 of 1939 contrasted with stronger dw of outer 1939 on figure 2, below; ddw 

 changing to a ce gl ; multii)licity. 

 1938 : see with wide ddw. 



1939: see with strong dw ; "outer thin" see with weak dw. 

 1940: Effects of natural frost; see with ddw becoming separate gl. 

 1941 : inc : cambium probably dead, killed by artificial freezing of May 9, 



1941. 

 Fig. 2. XSC ii-s-c. Branch section (> cm. outward from that of figure i, above. 



Xylem of 1938-1941. In contrast with figure I, dw of "outer thin" gl of 



1939 is much stronger ; multiplicity. 



1938: see with weak dw. 



1939: Inner gl with sharp dw which separates into 3 dilTuse bands; "outer 

 thin" gl here much wider and possessed of stronger dw than else- 

 where in this branch and in other branches. 



1940: see with heavy dw and irregular outer contact. 



1941 : inc; cambium dead, killed by artificial freezing of May 9, 1941. 



