280 KNUDSON : CAMBIUM DEVELOPMENT IN AMERICAN LARCH 



figures refer to tree A. The figures from June 3 to July 6 refer 

 to tree C. 



TABLE III 



NUMBER OF ROWS OF NEW XYLEM CELLS FORMED AND DIAMETER OF NEW XYLEM 

 TISSUE IN TREES A AND C 



From the table it cannot be determined exactly in which part 

 of the tree xylem growth first begins. The greatest growth by 

 June 3 was below the fifth whorl of branches while the least growth 

 was just below the first whorl of branches. In general, by June 

 3 more xylem cells were formed in the middle of..the tree than at 

 either the top or base. This would tend to indicate that the first 

 growth of xylem occurred in the middle of the tree below the fifth 

 whorl of branches. 



TABLE IV 



NUMBER OF ROWS OF NEW XYLEM CELLS AND DIAMETER OF NEW XYLEM TISSUE IN 



TREES B AND D 



