GOT) ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



Page. 



Phos])horic acid, investipalions 296-298 



PhotoLrrai)]nc work, Roads Office 522 



PhotDirraplip, output of illustrations section of Publications Division 400^01 



Photostats, copies of rare books, acquisition by library 432 



Phtbalic anhydride, jiroduclion and uses 278 



Pickering sprays, ex])eriments 276 



Pigeons, breeding investigations 105 



Pigs, lungworms infection, studies 150 



Pine- 

 beetles, depredations and control 321-323 



white, blister rust, caiises and control 211-215 



Pink bolhvorm. See BoUworm, pink. 

 Pipes — 



concrete, for irrigation, improvement 524 



metal, investigations 517 



Pisgah Game Preserve, law violations 584, 601 



Plague, bubonic, transmission by rats 353 



Plant- 

 Industry Bureau — 



librarv', work 437, 440 



report of chief 159-220 



work and organization, summary 159-161 



quarantines. See Quarantines, plant. 

 Plants- 

 chemistry, studies 273-274 



diseases — 



control work 27-28 



investigations 198-220 



entry, restrictive orders 638-640 



growth, daylight requirements 34 



importations, regulations 631-634 



inspection — 



and quarantine work 613-640 



port service 635 



new introductions, effect on agricultural industry 32 



nutrition investigations 161 



poisonous investigations 141-142, 193 



quarantine act — 



administration, and violations 578, 584, 589, 636 



amendments, recommendations 54 



Plodia interpunctelh , control in dried products 277 



Plumes, migratory bird, seizure for violation of law 373 



Plywood, glues, studies -_ 247 



PoixDEXTER, Senator, bill for survey of pulpwood resources, necessity 252 



Poisoning— 



by olives, study and control 260 



live stock, by plants, investigations 141-142 



rodents, cooperative work 347-352 



Poisonous plants investigations. 141-142, 193 



Poisons, cumulative effects, experiments 275 



Pork, soft, investigations 92, 98 



Porto Rico — 



cotton and products, entrv restrictions 623, 638 



experiment station, work,' 1920 456, 460-462 



Potash — 



recovery from kelp, experimental plant work 301-o0o 



requirements of potato, and cotton crops 196 



sources, development 40-41, 298-299, 301-305 



Potato- 

 crop, 1920, remarks by Secretary ^ 



plant, potash requirements 196 



wart, control, work of Horticultural Board 626-628, 638 



Potatoes — 



acreage and production, 1914-1920 5, o 



estimates, importance ^1^ 



