Occasional papers - San Diego Society of Natural History. (San Diego Society of Natural History, 1949)

Oecology of plants : an introduction to the study of plant-communities - Vahl, M. (Martin), 1749 -1804 (Clarendon Press, 1909)

Oecology of plants : an introduction to the study of plant-communities - Warming, Eugenius, 1841 -1924 (Clarendon Press, 1909)

Oecology of plants; an introduction to the study of plant-communities - Balfour, Isaac Bayley, 1853 -1922 (Clarendon Press, 1909)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1890)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1896)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1898)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1902)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1903)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1904)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1906)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1907)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1910)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1916)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1918)

Oesterreichische botanische Zeitschrift (A. Skofitz, 1920)

Ohio Biological Survey notes - Ohio Biological Survey. (Ohio Biological Survey, 2017)

The Ohio journal of science - Ohio Academy of Science. (Ohio Academy of Science, 1909)

The Ohio naturalist - Ohio Academy of Science. (Biological Club of the Ohio State University, 1910)

The Ohio naturalist - Ohio Academy of Science. (Biological Club of the Ohio State University, 1912)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1973)

Om Galapagos-hoarnes vegetation - Andersson, N. J. (Nils Johan), 1821 -1880 (Norstedt, 1857)

Om vegetationen paa de Dansk-Vestindiske er - Børgesen, Frederik, 1866 -1956 (E. Bojesen, 1898)

On the vegetation of the Bermudas - Jones, J. Matthew (John Matthew), 1828 -1888 (s.n, 1874)

The Ontario natural science bulletin - Wellington Field Naturalists' Club. (Wellington Field Naturalists' Club, 1905)

Opuscules de botanique (1862-1873) - Jussieu, Antoine Laurent de, 1748 -1836 (1875)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1904)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1908)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1909)

The Ottawa naturalist - Ottawa Field-Naturalists' Club (Ottawa Field-Naturalists' Club, 1910)

Our South African flora = Ons Suid-Afrikaanse plantegroei - Compton, R. H. (Cape Times, 1900)

An outline of plant geography (The Macmillan company, 1926)

Outline of the flora of Trinidad - Crüger, Herman, 1818 -1864 (Peter and Galpin, 1858)

Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) - Leavitt, Robert Greenleaf, 1865 - (American Book Co, 1901)

Palestine Exploration Fund : quarterly statement - Palestine Exploration Fund. (The Fund, 1885)

Pamphlets on forestry. Grazing (1900)

Pamphlets on forestry in Nebraska (1900)

The Pan-Pacific entomologist - Van Duzee, Edward P. (Edward Payson), 1861 -1940 (Pacific Coast Entomological Society, 1977)

Papers and botanical notebooks of Thomas Frederick Cheeseman, 1867-1923 - Cheeseman, T. F. (Thomas Frederick), 1846 -1923 (1887)

Papers and botanical notebooks of Thomas Frederick Cheeseman, 1867-1923 - Cheeseman, T. F. (Thomas Frederick), 1846 -1923 (1867)

Papers and proceedings of the Royal Society of Tasmania - Royal Society of Tasmania. (The Society, 1888)

Papers and proceedings of the Royal Society of Tasmania - Royal Society of Tasmania. (The Society, 1891)

Papers from the Tortugas Laboratory of the Carnegie Institution of Washington - Carnegie Institution of Washington. Department of Marine Biology. (Carnegie Institution of Washington, 1918)

Papers on cereal and forage insects. The timothy stem-borer, a new timothy insect [Mordellistena ustulata Lec.] - Phillips, William J. (Govt. Print. Off, 1911)

Papers presented at the Celebration of the Twentieth Anniversary of the New York Botanical Garden, September 6-9, 1915. Published by the aid of the David Lydig Fund, bequethed by Charles P. Daly - New York Botanical Garden (1916)

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

Part list of determinations of herbaceous plants of Liberia - Linder, David H. (David Hunt), 1899 -1946 (1926)

Pasture, meadow, and forage crops in Nebraska - Hitchcock, A. S. (Albert Spear), 1865 -1935 (G.P.O, 1904)

Pasture plants and pastures of New Zealand - Hilgendorf, F. W. 1874 -1942 (Whitcombe & Tombs, limited, 1918)

Patterson's numbered check-list of North American plants north of Mexico - Patterson, Harry N. (Harry Norton), 1853 -1919 (Patterson, 1892)

Perfil botánico-geológico de la carretera México-Acapulco - Mexico Secretaria de la Economia Nacional. Oficina de Geografia Economica (Talleres Gráficos de la Nación, 1935)

Pflanzen-geographie auf physiologischer Grundlage - Schimper, A. F. W. (Andreas Franz Wilhelm), 1856 -1901 (Gustav Fischer, 1908)

Pflanzenbiologische Untersuchungen : nebst algologischen Schluszbemerkungen - Hansgirg, Antonin, 1854 -1917 (Alfred Hölder, 1904)

Das Pflanzenreich :regni vegetablilis conspectus - Engler, Adolf, 1844 -1930 (W. Engelmann, 1911)

Die Pflanzenwelt Afrikas, insbesondere seiner tropischen Gebiete : Grundzge der Pflanzenverbreitung im Afrika und die Charakterpflanzen Afrikas - Engler, Adolf, 1844 -1930 (W. Engelman, 1910)

Die Pflanzenwelt der peruanischen Anden in ihren Grundzügen dargestellt - Weberbauer, A. (August), 1871 -1948 (W. Engelmann, 1911)

Die Pflanzenwelt Ost-Afrikas und der Nachbargebiete - Engler, Adolf, 1844 -1930 (D. Reimer, 1895)

Die Pflanzenwelt von West-Australien südlich des Wendekreises. Mit einer Einleitung über die Pflanzenwelt Gesamt-Australiens in Grundzügen. Ergebnisse einer im Auftrag der Humboldt-Stiftung der Kgl. Preussischen Akademie der Wissenschaften, 1900-1902 unternommenen Reise - Diels, Ludwig, 1874 -1945 (W. Engelmann, 1906)

Phalaridea - Trinius, Carl Bernhard, 1778 -1844 (Typis Academiae Caesareae Scientiarum, 1839)

Phanerogamic flora of the divisions of Uitenhage and Port Elizabeth : with a sketch map - Schönland, S. 1860 - (Govt. Print. and Stationery Office, 1919)

Philippine fiber plants - Brown, William Henry, 1884 -1939 (Bureau of Printing, 1919)

The Philippine journal of science - Philippines. National Science Development Board. (Bureau of Science, 1906)

The Philippine journal of science - Philippines. National Science Development Board. (Bureau of Science, 1910)

The Philippine journal of science - Philippines. National Science Development Board. (Bureau of Science, 1914)

The Philippine journal of science - Philippines. National Science Development Board. (Bureau of Science, 1915)

The Philippine journal of science - Philippines. National Science Development Board. (Bureau of Science, 1916)

Physis - Sociedad Argentina de Ciencias Naturales. (Asociación Argentina de Ciencias Naturales [etc.], 1915)

Physis - Sociedad Argentina de Ciencias Naturales. (Asociación Argentina de Ciencias Naturales [etc.], 1921)

Phyto-edaphic communities of the Upper Rio Puerco Watershed, New Mexico - Francis, Richard E. (U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, 1986)

Phytogeographic survey of North America. A consideration of the phytogeography of the North American continent, including Mexico, Central America and the West Indies, together with the evolution of North American plant distribution - Harshberger, John W. (John William), 1869 -1929 (W. Engelmann, 1911)

Phytogeography of Nebraska. 1. General survey by Roscoe Pound and Frederic E. Clements - Clements, Frederic E. (Frederic Edward), 1874 -1945 (Published by the Seminar, 1900)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1964)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1966)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1968)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1970)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1971)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1972)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1975)

Phytologia - Moldenke, Harold N. (Harold Norman), 1909 -1996 (H.A. Gleason and H.N. Moldenke, 1976)