MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 297 



entries are cited from the notes accompanying the auxographic 

 tracings : 



Elongating at 12° C. and below on March 2, with the air at about 



Fig. I. Joints of Opuniia Sp. The youngest stage at which growth 

 measurements were begun is illustrated by the small figure at the bottom. 

 Successive stages are denoted by size. The largest figure is that of a mature 

 joint bearing flower buds. Longitudinal section of joint on the right. Growth 

 throughout the entire joint during its development is denoted by the increas- 

 ing distances between the nodes denoted by the clusters of spines. About 

 one third actual size. 



the same temperature: Elongation began on March 23, after a 

 night of shortening, at a temperature of 18° C, and under similar 

 conditions, but with air temperature falling to 9° C. growth began 



