Vol. VII 
NOVEMBER, 1920 
No. 9 
AMERICAN 
JOURNAL OF BOTANY 
OFFICIAL PUBLICATION OF THE 
BOTANICAL SOCIETY OF AMERICA 
DEC8 
CONTENTS 
The cambium and its derivative tissues. II. Size variations of cambial initials 
in gymnosperms and angiosperms I. W. Bailey 355 
An apparatus for determining small amounts of carbon dioxide 
R. C. Wright 368 
The secretion of invertase by plant roots .......... Knudson 371 
Daily rhythms of elongation and cell division in certain roots 
Ray C. Friesner 380 
PUBLISHED 
IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA 
At 41 North Queen Street, Lancaster, Pa 
BY THE 
BROOKLYN BOTANIC GARDEN 
Brooklyn, N. Y. 
Entered as second-class matter February 21, 1914, at the post office at Lancaster, Pennsylvania, 
under the act of March 3, 1879 
