Oesterreichische botanische Zeitschrift (A. Skofitz, 1918)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1883)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1884)

Orange rust of raspberry and blackberry - Schneider, Albert, 1863 -1928 (University of Illinois Agricultural Experiment Station, 1893)

The Orchid review (Orchid Review ltd.], 1900)

Die Orchideen :ihre Beschreibung, Kultur und Zu¨chtung. Handbuch fu¨r Orchideenliebhaber, Zu¨chter und Botaniker - Schlechter, Rudolf, 1872 -1925 (P. Parey, 1915)

Orchis :Monatsschrift der Deutschen Gesellschaft für Orchideenkunde - Dammer, Udo. (1915)

Outlines of British fungology; containing characters of above a thousand species of Fungi, and a complete list of all that have been described as natives of the British Isles - Berkeley, M. J. (Miles Joseph), 1803 -1889 (L. Reeve, 1860)

Outlines of classification and special morphology of plants - Balfour, Isaac Bayley, 1853 -1922 (Clarendon Press, 1887)

Outlines of classification and special morphology of plants - Goebel, K. (Karl), 1855 -1932 (Clarendon Press, 1887)

Oversigt over det Kongelige Danske videnskabernes selskabs forhandlinger = Bulletin de l'Académie royale des sciences et des lettres de Danemark - Kongelige Danske videnskabernes selskab. (A.F. Høst, 1884)

Oversigt over det Kongelige Danske videnskabernes selskabs forhandlinger = Bulletin de l'Académie royale des sciences et des lettres de Danemark - Kongelige Danske videnskabernes selskab. (A.F. Høst, 1896)

Pamietnik Fizyjograficzny (Druk K. Kowalewskiego, 1914)

Pamietnik Fizyjograficzny (Druk K. Kowalewskiego, 1916)

Pamietnik Fizyjograficzny (Druk K. Kowalewskiego, 1918)

Pamphlets on forestry in Nebraska (1900)

Pamphlets on forestry in North Dakota and South Dakota (1900)

Pamphlets on silviculture (1899)

The Pan-Pacific entomologist - Van Duzee, Edward P. (Edward Payson), 1861 -1940 (Pacific Coast Entomological Society, 1985)

Parasitic fungi of Illinois / by T.J. Burrill - Earle, F. S. (Franklin Sumner), 1856 -1929 (J. W. Franks, 1885)

I parassiti vegetali delle piante coltivate od utili - Ferraris, Teodoro. (Sineo & Bo, 1913)

Part I. The living flora of West Virginia - Millspaugh, Charles Frederick, 1854 -1923 (Wheeling news litho. co, 1913)

Patologia vegetale. Fanerogame parassite, mixomiceti, bacterii, ifomiceti od eumiceti (funghi) - Voglino, Pietro. (Unione tipografico-editrice [Gia ditta Pomba e c], 1905)

Penjing plants from China : Buxus sinica, Ehretia microphylla, Podocarpus macrophyllus, Sageretia thea, Serissa foetida - United States. Animal; Plant Health Inspection Service. Plant Protection; Quarantine Programs. Biological Assessment; Taxonomic Support. (Biological Assessment and Taxonomic Support, Plant Protection and Quarantine, Animal and Plant Health Inspection Service, U.S. Dept. of Agriculture, 1996)

Pesticides documentation bulletin - National Agricultural Library (U.S.) (National Agricultural Library, U.S. Dept. of Agriculture, #c 1965-1969, 1965)