Vol. VI. APRIL, 1919 No. 4 
AMERICAN 
JOURNAL OF BOTANY 
OFFICIAL PUBLICATION OF THE 
BOTANICAL SOCIETY OF AMERICA 
CONTENTS 
The influence of light upon the action of stomata and its relation to the trans- 
piration of certain grains John Gray and George J. Peirce 131 
The origin and nature of the mucilage in the cacti and in certain other 
plants , Francis E. Lloyd 156 
The influence of phosphates on the action of alpha-crotonic acid on plants. 
J. J. Skinner and F. R. Reid 167 
PUBLISHED 
IN COOPERATION WITH THE BOTANICAL SOCIETY OF AMERICA 
BY THE 
BROOKLYN BOTANIC GARDEN 
At 41 North Queen Street, Lancaster, Pa. 
Entered as second-class matter February 21, 1914, at the post office at Lancaster, Pennsylvania, 
under the act of March 3, 1879 
