Plate ii 



Fig. I. TTC 12-14-b. Detail of figure 2, plate 10. Xylem of 1944-1945. Mature 



cells as striking example of psg. 



1944: see with dw i-cell tiiick. 



1945: see with dw i to 2 cells thick; psg of mature cells added outside the 

 normal 1945 growth. 

 Fig. 2. TTC 12-14-C. Branch section of Cuprcssus arizonica, cut November 17, 



1945. Xylem of 1943-1945. Dw i-cell thick; dw which resembles ilw. 



1943 : see whose dw is i to 2 cells thick. 



1944: see with 2 Iw cells and 1-2 dw cells. Dw appears to be ilw attached 

 to 1945. 



1945 : see with irregular outer margin ; scattered mature cells of psg. 

 Fig. 3. TTC 30-i-b. Branch section of Cuprcssus arizonica, cut November 4, 



1939. Xylem of 1939. Annual increment with indefinite margin, indefinite 



dw, and psg. Incipient dw (poorly developed and dififuse) followed radially 



by large nucleated immature cells, the psg. Had this branch grown another 



year before sectioning, one would have difficulty in determining the outer 



margin of 1939 growth. 



