192 AN"]SrUAL EEPOETS OP DEPARTMENT OF AGEICULTURE. 



their natural or usual habitats, and the changes induced by them in 

 foodstuffs. With this was combined a study of related forms. The 

 results of the study of the Penicillium luteum purpurogenum group 

 have been published. A study of corn silage and corn meal was 

 begun. This work supplements work previously completed and pub- 

 lished in Department Bulletin No. 215, " Composition of Corn 

 (Maize) Meal Manufactured by Different Processes and the Influence 

 of Composition on the Keeping Qualities." 



^ Plant chemistry. — To form a basis for practical nutrition inves- 

 tigations the composition of vegetable proteins and the forms in 

 which nitrogen occurs in plants were studied. The prussic-acid 

 content of various forage and medicinal plants was determined 

 by an improved method which has been published. Among other 

 plant chemical problems, the properties of saponin and saponin- 

 bearing plants were investigated, and special attention was given to 

 medicinal plants containing emodin for the purpose of improving 

 analytical methods. A new volatile oil has been isolated from the 

 flowers of the cotton plant and examinations have been made of the 

 glucoside found in its leaves. The work done by the bureau in con- 

 nection with this plant was for the purpose of assisting the Bureau 

 of Entomology in its boll-weevil investigations. 



Analyses were made of the different varieties of American forage 

 grasses, and a report on their composition was made to the Bureau 

 of Plant Industry for use in the preparation of the bulletin, " Native 

 Pasture Grasses of the United States." 



Investigations of the bureau in connection with the production, 

 botanical composition, and volatile-oil strength of American wild 

 mustard seed and the hydrogen number of the essential oils of 

 sassafras, anise, fennel, clove, and pimenta have been published. 



Vegetables and fruits. — Experiments in the drying of potatoes 

 on a commercial scale were begun during the year. Preliminary ex- 

 periments were made in methods of manufacturing potato starch, 

 glucose, and dextrin and in practical methods of ensiling potatoes. 

 The propagation of desirable lactic-acid bacteria for inoculation of 

 ensilage was commenced. 



Some of the results of the experiments and investigations in con- 

 nection with the utilization of surplus fruit were published in De- 

 partment Bulletin 241, " Studies on Fruit Juices," and in a Yearbook 

 article on "Apple Sirup and Concentrated Cider." 



Studies were continued in California on the ripening of oranges. 

 A tentative standard for determining maturity, based upon the ratio 

 of acids to solids, proposed by the bureau, was generally adopted by 

 the orange growers. 



Attention was given to the development of methods of manufac- 

 turing citric acid, lemon oil, orange juice, orange vinegar, and other 

 by-products of citrus fruits. 



In cooperation with the Bureau of Plant Industry the composition 

 of oranges and lemons from selected trees was determined, with the 

 object of making selections in propagation experiments. 



Investigations of the mottled-leaf disease of citrus trees, in co- 

 operation with that bureau, demonstrated that such trees, in addi- 

 tion to lime, require considerable organic matter, which may be best 

 supplied through green manuring. 



