Nov. i, 1920 Composition of Normal and Mottled Citrus Leaves 1 83 



These data show that the expressed sap of mature orange leaves is 

 comparatively rich in solids, calcium, and potassium, but the ratio of 

 calcium to potassium in the sap is widely different from the ratio of the 

 total amounts of these elements in the leaf. (Table II.) 



On June 5, 191 8, three sets of samples of Valencia orange leaves were 

 collected. One of these was composed of normal leaves about 6 weeks 

 of age; another sample obtained from the same trees consisted of healthy 

 mature leaves; whereas the third sample was chosen to represent severely 

 mottled leaves of the previous year's growth. Each of the samples was 

 divided into three parts, one of which was used to study the sap, another 

 to determine the water-soluble constituents, and the third for total 

 analysis. 



The sap was pressed out after freezing as described above. The water- 

 soluble constituents were extracted by first grinding 100 gm. of the fresh 

 leaves in a meat grinder, shaking with 1 ,000 cc. distilled water for one hour, 

 and filtering through filter paper. Total acidity was determined by titra- 

 tion with N/io sodium hydroxid, using phenolphthalein as indicator. 

 It was necessary to dilute the sap considerably because of its dark color, 

 and a high degree of accuracy is not claimed for the results. They are 

 rather approximations. The acidity is expressed for convenience as 

 anhydrous citric acid. 1 The results are presented in Tables XVI, XVII, 

 and XVIII. 



Table XVI. — Composition of Valencia orange leaves at the age of 6 weeks 



a Expressed in terms of dry matter. 

 Table XVII. — Composition of normal mature Valencia leaves 



° Expressed in terms of dry matter. 



1 The nature of the acid constituents of the leaves has not been investigated sufficiently to justify a 

 definite statement as to their identity. 



