Oak - 6 clippings
Oats - 2 clippings
Ochroma - 12 clippings, including Boston Traveler 1942 "Balsa is Vital to War Effort".
Ocimum - 4 clippings, including The Agricultural News 1904 "A Victim of the Mosquito Plant".
Oenothera - 4 clippings
Oils 1.1 (up to 1910's) - 19 clippings, including American Food Journal 1912 "The Shea Butter of Africa".
Oils 1.2 (1910's) - 16 clippings, including U.S. Commerce Reports 1918 "New Oil Seed from the Kongo".
Oils 1.3 (1910's) - 6 items, including Scientific American 1919 "Using Vegetable Seeds".
Oils 2.1 (1920's - 1930's) - 21 clippings
Oils 2.2 (1920's - 1930's) - 28 clippings, including Boston Evening Transcript 1936 "Germ-Killing Oil Distilled from Australian Tree".
Oils 3 (1940's - 1950's) - 14 items
Oils 3.2 - 8 items
Oil Seeds - 15 items
Okra - 2 items
Olea - 15 clippings, including Smithsonian 1985 "One of Nature's Greatest Gifts to Man".
Olearia - 4 clippings
Onion - 11 items, including Boston Traveler 1939 "Onions, Garlic and Horse Radish Seen Potential Deadly Enemies of Disease".
Opium 1 (up to 1920's) - 10 items, including The Boston Globe 1928 "Customs men seize $1,000,000 in Opium".
Opium 2 (1930's-1940's) - 13 items, including The Boston Sunday Post 1936 "Opium Ban Cost 25 Millions".
Opium 3 (1950) - 1 item
Opium 4 (1960's - 1980's) - 22 clippings, including Orientations 1979 "Old China's Opium Boxes", High Times 1982 "Master Addicts".
Opuntia - 10 clippings, including The Garden Magazine 1908 "The Oldest Flowers in Cultivation".
Oral Hygiene - 1 clipping
Oranges - 32 clippings, including Scientific American Monthly 1921 "The Perfume of the Orange".
Orchids - 19 items, including The New York Times 1972 "Orchids are Tested as Contraceptive".
Ordeal Poison - 1 clipping
Oreodoxa - 2 clippings
Ornamental Seeds - 2 clippings
Ornamental Plants - 9 items
Oroxylon - 1 clipping
Orthostemon - 3 clippings
Ostrya - 2 clippings
Oxalis - 3 items