1 62 Journal of Agricultural Research voi.xx,No. 3 



In connection with investigations on the nutrition of different species 

 of citrus trees, especially as related to that condition known as mottle- 

 leaf, we have determined the composition of different parts of the tree, 

 such, for example, as the roots, old wood, young wood, leaves, leaf sap, 

 and fruit. This work has extended over a period of several years, and 

 further study is contemplated. Some of the results already obtained 

 have proved to be of special interest. The present paper will be devoted 

 mainly to a discussion of the composition of the leaves. 



It is not necessary to review the many published analyses of citrus 

 fruits. Most of the publications on this subject have dealt mainly with 

 the organic constituents and total ash, with an occasional analysis of 

 the ash. Comparatively few analyses have been published showing the 

 composition of portions of citrus trees other than the fruit. 



The earliest investigation we have been able to find, and perhaps the 

 best known, is that of Rowney and How {15) 1 , published in 1848. Anal- 

 yses were reported of the roots, stems, leaves, and fruit of orange trees, 

 Citrus aurantium, grown on the island of St. Michael. The variety was 

 presumably that now known as St. Michael. 2 The analyses were ex- 

 pressed as percentages of the carbon-dioxid-free ash. The results were 

 similar to our analyses of California orange trees, when calculated to the 

 same basis. 



In 1 891 Oliveri and Guerrieri (13) published an extended study on the 

 composition of the wood, leaves, and different portions of the fruit of 

 the orange, Citrus aurantium Riss; 2 Mandarin, C. nobilis var. deliciosa, 

 Swingle; and lemon, C. limonia Osbeck, grown in Palermo, Italy. This 

 investigation, extending over a period of three years, is the most com- 

 plete study yet published on the composition of different parts of citrus 

 trees. They recorded the number and weights of fruits produced by 

 different classes of trees and the number and weights of leaves and the 

 weights of wood pruned from the trees during a period of three years, 

 representative samples of which were analyzed. Some of their analyses 

 also agree reasonably closely with our data. 



In 1 001 Alino (1) determined the phosphoric acid, potash, and nitrogen 

 content of orange wood, leaves, and fruit; and in 1909 Muller (12) pub- 

 lished complete analyses of seedling orange leaves from healthy and 

 diseased trees grown in South Africa. 



In 1 910 Blair (2) analyzed orange leaves and stems grown in Florida. 

 His samples represented the new growth taken in October from certain 

 plots of a fertilizer experiment. In 1917 Jensen (7) published a paper 

 on the composition of normal and mottled orange, lemon, and grape- 



1 Reference is made by number (italic) to "Literature cited," p. 190-191. 



2 In this case, the sweet orange. Citrus sinensis Osbeck, is doubtless the species studied. W. T. 

 Swingle's revision of citrus nomenclature, as given in the "American Standard Cyclopedia of Horticulture," 

 is followed in this paper. 



