EXPERIMENTAL METHODS. 



23 



ently fully turgid. Repeated tests did not indicate any definite correlation 

 between color and acidity, as no distinct acidity difference appeared between 

 red and green shoots from any one plant. Inasmuch as the dry plants are 

 more often red than not and the turgid ones usually green, there may be some 

 connection which the writer failed to discover. It is not impossible that a 

 diminished water-supply may influence the formation of anthocyan in the 

 epidermis of this species. It would be an interesting question to determine, 

 but would take a closer study of this particular point than could be here 

 attempted. Record was consistently made on plant color, but no data were 

 assembled that could justify a more definite statement than the above. 



Since it was obviously necessary to remove the joints from the plant for 

 purposes of experimentation, it became important to ascertain if the wounding 

 incident upon removal induced any traumatic reaction that affected either 

 respiration or acidity. Various experiments were made which showed that 

 so slight an injury as that occasioned by detaching the joints produced no 

 important effect. The averages of four series made in March 1911, showing 

 both the total and pure-juice acidity, give a slightly higher result for the former 

 and practically an identical result for the latter, as is shown in table 4. Refer- 

 ence to the itemized record in table 7 shows, however, that while the acidity 

 was higher in the detached joints in two experiments, it was lower in the other 

 two. The variations are not more than are to be expected from individual 

 differences without reference to the question of wounding, and may be con- 

 sidered negligible. 



TABLE 4. Average of four series showing acidity of attached and removed joints, March 1911. 



The same results were obtained from a series of four experiments made in 

 July 1912, in which only the acidity of the juice was determined. The normal 

 rise and fall of acidity is given according to the time of day at which the 

 determination was made, as is shown in table 5. 



TABLE 5. Average of four series of juice acidity in attached and removed joints, July 1912. 



