Nov. 1. 19:10 Composition of Normal and Mottled Citrus Leaves 165 



phosphoric acid were precipitated collectively by adding a weighed 

 excess of ferric chlorid, neutralizing with ammonia, filtering, redissolving 

 in dilute hydrochloric acid, and repeating the process. Iron was pre- 

 cipitated with ammonia from a separate aliquot and determined volu- 

 metrically by reduction with zinc and titration with permanganate. 

 This method was occasionally supplemented by the ferrocyanid colori- 

 metric method with fairly satisfactory results. Aluminum was calculated 

 by difference after the phosphoric acid was gravimetrically determined 

 in a separate aliquot. Calcium, magnesium, potassium, and sodium were 

 determined in the filtrate after the ammonia precipitate was removed, 

 and in some cases manganese was determined by bromin oxidation. 

 Sulphate was determined gravimetrically in an aliquot of the original 

 solution. Carbon dioxid was not determined. 



COMPOSITION OF NORMAL MATURE ORANGE LEAVES 



A considerable number of analyses have been made of mature orange 

 leaves representing both the Washington Navel and Valencia varieties. 

 Owing to the absence of previous records showing the age of the leaves 

 available for analysis, and in view of the fact that orange leaves, when 

 from 4 to 6 months of age, assume an appearance not unlike that of 

 leaves 1, 2, or more years of age, it is highly probable that random sam- 

 ples will always represent mixed ages. 1 Most of our samples of mature 

 leaves were taken at random, always avoiding immature or abnormal 

 individuals. The samples were gathered at different seasons of the 

 year and from a considerable number of different sets of trees, some of 

 which were growing in different localities. Typical analyses are sub- 

 mitted in Tables I and II. 



It is interesting to note that the composition of the different samples 

 was found to be reasonably uniform despite the fact that their average ages, 

 although they were mature in appearance, probably varied considerably. 

 Other samples not reported above showed a similar composition. The data 

 also afford but little evidence of seasonal variation in composition. 



Except in calcium and potassium content, the different samples of 

 the same variety differed almost as widely in composition as the samples 

 of different varieties. The samples from different localities were also 

 similar in composition, although those from Riverside were grown on 

 sandy loam soil, that from Anaheim on light sandy soil, and the one from 

 Whittier on heavy adobe. 



It will be noted that the average calcium content of Valencia leaves 

 was found to be somewhat higher than that of Navels, while the reverse 

 is true for potassium. 



'Ensign (<5) has recently shown that the size of the vein islets of Citrus grandis is directly correlated with 

 the maturity of the leaf. From the most immature to fully matured leaves there is a gradual increase in 

 the size of the vein islets. If further investigation prove that similar relations occur in other species of 

 citrus, a direct means will be afforded by which the age of the leaves can be determined. 



