22 BULLETINS OF THE BUREAU OF PLANT INDUSTRY. 



functions of mineral substances; general value of certain mineral salts; the 

 low atomic weight of the mineral nutrients — The physiological role of phos- 

 phoric acid : Eelation of phosphoric acid to proteids and to the division of 

 cells ; the physiological importance of lecithin ; jihosphoric acid in chloro- 

 phyll ; potassium phosphate as a cell constituent — The jihysiological role of 

 silica — The physiological role of iron compounds : Relation between the 

 coloring matter of the blood and of the leaf ; influence of iron and other 

 mineral nutrients on the formation of chloroi^hyll ; fertilizing Effect of iron 

 salts ; organic compounds containing iron ; iron in fungi ; manganese in 

 plants — The physiological role of halogen compounds : Plants raised without 

 chlorids ; value of potassium chlorid for buckwheat ; beneficial and injurious 

 action of chlorids ; absorption of chlorids by aquatic plants ; sodium chlorid 

 in animals; fluorids in physiological relations; behavior of plants to potas- 

 sium bromid ; relations of organisms to iodin compounds — The physiological 

 role of alkali salts : Importance of jjotassium for the formation of starch and 

 protein ; beneficial action of soclium salts upon plants ; necessity of sodium 

 salts for animals ; can potassium salts be replaced by rubidium salts in green 

 plants and in animals?; behavior of fungi toward rubidium salts; physiolog- 

 ical superiority of potassium salts — The physiological role of calcium and mag- 

 nesium salts : Distribution of lime and magnesia in plants ; the jahysiological 

 importance of lime salts in plants ; views on the functions of lime salts ; 

 formation of lime incrustations ; can calcium in plant cells be replaced by 

 strontium?; poisonous action of magnesium salts; life without lime salts; 

 possible relations between lime and the transportation of starch ; the x^hysi- 

 ological role of magnesium salts ; increase of magnesia in oily seeds ; neces- 

 sity of magnesium salts for fungi ; can magnesium salts be replaced by 

 beryllium salts?; importance of lime salts for animals; proportions of lime 

 and magnesia in animal organisms ; behavior of animals to strontium salts 

 and oxalates ; final remarks. 



* No. 46. The Propcagation of Tropical Fruit Trees and Other Plants. 



By George W. Oliver, Expert. 1903. 28 pp., 8 pis. 



Price, 10 cents. 



Contents : Introduction — The mango : Prospects as a fruit tree ; propa- 

 gation in India ; propagating tests at the Department ; best age for wood ; 

 thick bark of mango an obstacle in budding; knife for budding the mango; 

 methods which show best results ; applying the buds ; when to bud ; selection 

 of budding material ; a second method of attaching the bud ; raising seedling 

 stocks ; transplanting young seedlings ; importing mango scions — The loquat : 

 Regions where the loquat may be grown ; raising seedling stocks — The fig : 

 Cuttings ; grafting and budding — Tea : Necessity for vegetative propagation ; 

 veneer grafting ; herbaceous grafting ; propagating house ; cuttings — Manila 

 hemp: Importance of introduction into the United States; raising plants 

 from seeds ; cultivation in the Philippine Islands — Description of plates. 



* No. 47. The Description of Wheat Varieties. By Carl S. Scofield, 



Botanist in Charge of Grain Grade Investigations. 1903. 



19 pp., 1 folding table, 7 pis. Price, 10 cents. 



Contents : Introduction — Explanation of form used in the description of 

 wheat varieties — Description of plates. 



No. 48. The Apple in Cold Storage. By G. Harold Powell, Assistant 

 Pomologist in Charge of Field Investigations, and S. H. 

 Fulton, Assistant in Pomology. 1903. 66 pp., 6 pis. (in- 

 cluding 5 in colors). Price, 15 cents. 



Contents : Introduction — Influence of cold storage on the apple industrj- — 

 The extent of the cold-storage warehousing industry — The function of the 

 cold-storage warehouse — Principles of mechanical refrigeration : Tlie utiliza- 

 tion of the cold temperatures; the direct-expansion system; the brine- 

 circulating system ; the air-circidating system — Outline of experiments in 

 apple storage — Factors influencing the keei^ing quality of apples : The maturity 



101 



