140 



Hydration and Growth. 



Opuntia, March 25 to April 24. 



in weight of disk-shaped sections taken from the joints at sunrise and 

 sunset, with the results shown in table 106. (Fig. 30.) 



These results afford a comparison only between conditions at the 

 beginning and end of the daylight period and the time of the maximum 

 and minimum imbibition capacity was not determined as in Mesem- 

 bryanthemum. (See p. 145). Mr. Long 



also tested the effects of acids, hy- TABLE 107. Growth of flower-buds of 



droxids, and salts upon the growth of 

 Opuntia. Preparations for this purpose 

 consisted of mature joints bearing 

 young flower-buds. The bases of the 

 joints were suspended with their 

 freshly cut surfaces in solutions in 

 glass jars, and the lengths of the buds 

 were taken at intervals of 3 or 4 days. 

 The final amount of growth in each 

 case is given in table 107. (Fig. 31.) 1 



m. 12p.m. 



IZp.rn. m. 12p.m. m. 12p.m. m. 12p.m. m. 12p.m. 



12p.m. 



m. 12p.m. m. 12p.m. m. 12 p.m. rn^ 12p.m. 



12 p.m. m. 12 p.m. m. i2p.m. 



m. 12p.m. m. \2p.m. m. 12p.m. m. 12p. 



m. 12p.m. 



12p.m. 



FIG. 29. Continuation of record of variations in length of mature joint of Opuntia (see fig. 28) 

 amplified 50 times. The amplitude of the daily variations has been reduced to a minimum 

 November to January, with a general shrinkage in length. Equable conditions accompanying 

 clouds and rain are illustrated by the record of the week beginning January 15, 1917. The 

 influence of the advancing temperatures in inducing increased imbibition is illustrated by 

 the records of February to April, and a balance of daily losses and gains occurred about the 

 end of April. 



1 Long, E. R. Growth and colloid hydratation in cacti. Bot. Gaz., 59: No. 6. 1915. 



