SEASONAL VARIATIONS IN THE CARBOHYDRATE-CONTENT. 51 



plant. It was found that individual plants vary considerably in their sugar- 

 content, although the general course of the economy runs parallel. The 

 methods of the preparation of the material and analysis have already been 

 described. In table 13 are given the results of analyses of Opuntia phcea- 

 cantha during the months indicated in 1916. 



TABLE 13. Seasonal variation in carbohydrate-content. Analyses expressed in per 

 cent of the dry material. 



Although the values given in table 13 indicate the nature of the changes 

 in the various sugars under different external conditions, the facts are more 

 clearly expressed as proportional values. The factor of the synthesis of 

 the carbohydrates is an exceedingly complex one and can not be dealt with 

 here, so that variations in total sugar-content are of little significance for the 

 present purpose. The influence of the external conditions on the propor- 

 tional values will be brought out more clearly in the section dealing with 

 the special influence of water-content and temperature where the factor of 

 synthesis plays no role, as the plants were left in the dark and at constant 

 temperature. 



In table 14 the results of table 13 are given, calculated as proportional 

 values. 



TABLE 14. Proportional values of the carbohydrate-content of Opuntia phcvacantha 

 on the basis of the analysis of the dry material. 



