The problem of Krakatao as seen by a botanist - Backer, C. A. (Cornelis Andries), 1874 -1963 (The author, 1900)

Problems of cytology and evolution in the Pteridophyta - Manton, I. (University Press, 1950)

Proceedings - Cambridge Philosophical Society Mathematical and physical sciences - Cambridge Philosophical Society. (Cambridge Philosophical Society [etc.], 1902)

Proceedings - Cambridge Philosophical Society Mathematical and physical sciences - Cambridge Philosophical Society. (Cambridge Philosophical Society [etc.], 1910)

Proceedings of the Academy of Natural Sciences of Philadelphia - Academy of Natural Sciences of Philadelphia. (Academy of Natural Sciences of Philadelphia, 1856)

Proceedings of the Biological Society of Washington - Smithsonian Institution (Biological Society of Washington, 1922)

Proceedings of the Biological Society of Washington - Smithsonian Institution (Biological Society of Washington, 1924)

Proceedings of the Biological Society of Washington - Smithsonian Institution (Biological Society of Washington, 1933)

Proceedings of the Biological Society of Washington - Smithsonian Institution (Biological Society of Washington, 1938)

Proceedings of the Biological Society of Washington - Smithsonian Institution (Biological Society of Washington, 1947)

Proceedings of the Boston Society of Natural History - Boston Society of Natural History. (Boston Society of Natural History, 1903)

Proceedings of the Boston Society of Natural History - Boston Society of Natural History. (Boston Society of Natural History, 1907)

Proceedings of the California Academy of Sciences, 4th series - California Academy of Sciences (California Academy of Sciences, 2006)

The Proceedings of the Iowa Academy of Science - Iowa Academy of Science (The Academy, 1914)

Proceedings of the Linnean Society of London - Linnean Society of London. (Published for the Linnean Society of London by Academic Press [etc.], 1919)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1925)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1934)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1936)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1937)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1938)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1939)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1949)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1989)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 1992)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 2007)

Proceedings of the Linnean Society of New South Wales - Linnean Society of New South Wales. (Linnean Society of New South Wales, 2018)

Proceedings of the National Academy of Sciences of the United States of America - National Academy of Sciences (U.S.) (National Academy of Sciences [etc.], 1917)

Proceedings of the Royal Society of London - Royal Society (Great Britain) (The Society, 1888)

Proceedings of the Royal Society of London - Royal Society (Great Britain) (The Society, 1899)

Proceedings of the Royal Society of London - Royal Society (Great Britain) (The Society, 1902)

The Proceedings of the Royal Society of Queensland - Royal Society of Queensland. (Royal Society of Queensland], 2011)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1933)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1954)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1957)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1964)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1969)

Proceedings of the Royal Society of Victoria. New series - Royal Society of Victoria (Melbourne, Vic.) (Stillwell and Co, 1971)

Proceedings of the United States National Museum - Smithsonian Institution (Smithsonian Institution Press, [etc.], 1929)

Prodromus florae Norfolkicae, sive, Catalogus stirpium quae in Insula Norfolk annis 1804 et 1805 a Ferdinando Bauer collectae et depictae nunc in Museo Caesareo Palatino Rerum Naturalium Vindobonae servantur - Endlicher, Stephan, 1804 -1849 (Apud Fridericum Beck, 1833)

Progressus rei botanicae = Fortschritte der Botanik = Progrès de la botanique = Progress of botany - Association internationale des botanistes. (G. Fischer, 1914)

Pteridologia : a publication of the American Fern Society - American Fern Society. (The Society, 1989)

Pteridologia : a publication of the American Fern Society - American Fern Society. (The Society, 2002)

Pteridologia : a publication of the American Fern Society - American Fern Society. (The Society, 2007)

Pteridologist - British Pteridological Society. (The Society, 1986)

Pteridologist - British Pteridological Society. (The Society, 1987)

Pteridologist - British Pteridological Society. (The Society, 2002)

Pteridologist - British Pteridological Society. (The Society, 2005)

Pteridologist - British Pteridological Society. (The Society, 2010)

Pteridologist - British Pteridological Society. (The Society, 2012)

Pteridologist - British Pteridological Society. (The Society, 2013)

Pteridologist - British Pteridological Society. (The Society, 2008)

Pteridologist - British Pteridological Society. (The Society, 2015)

Pteridologist - British Pteridological Society. (The Society, 2016)

Pteridophyten - Christ, H. (Hermann), 1833 -1933 (Wilhelm Engelmann, 1896)

Ptéridophytes - Tardieu-Blot, Mme., (Laure) 1902 -1998 (1969)

Ptéridophytes : suivis d'une carte des localités du Gabon - Hallé, Nicolas (1964)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1930)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1929)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1940)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1931)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1936)

Publication. Field Museum of Natural History Botanical series - Field Museum of Natural History. (Field Museum of Natural History, 1939)

Publication - Smithsonian Institution. Institute of Social Anthropology (U.S. Govt. Print. Off, 1947)

Rapid biological inventories - Field Museum of Natural History. Environmental; Conservation Programs. (Field Museum, 2002)

Rapid biological inventories - Field Museum of Natural History. Environmental; Conservation Programs. (Field Museum, 2003)

Rapid biological inventories - Field Museum of Natural History. Environmental; Conservation Programs. (Field Museum, 2006)

Rapid biological inventories - Field Museum of Natural History. Environmental; Conservation Programs. (Field Museum, 2005)

Rare and endangered plants of Puerto Rico : a committee report - United States. Soil Conservation Service. (U.S. Dept. of Agriculture, Soil Conservation Service in cooperation with the Department of Natural Resources, Commonwealth of Puerto Rico, 1975)

Rare and endemic trees of Puerto Rico and the Virgin Islands - United States. Forest Service. (U.S. Dept. of Agriculture, Forest Service, 1980)

Rare and Threatened Plants of Cuba: ex-situ conservation in Botanic gardens (1989)

Records of the Auckland Institute and Museum - Auckland Institute; Museum. (Auckland Institute and Museum, 1931)

Records of the Auckland Institute and Museum - Auckland Institute; Museum. (Auckland Institute and Museum, 1948)

Records of the Queen Victoria Museum Launceston - Queen Victoria Museum (Launceston, Tas.) (The Museum, 1996)

Records of the Queen Victoria Museum Launceston - Queen Victoria Museum (Launceston, Tas.) (The Museum, 2003)

Regiones terrestres prioritarias de México - Aguilar Zúñiga, Claudia (Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO), 2000)

Reise der o¨sterreichischen Fregatte Novara um die Erde in den Jahren 1857, 1858, 1859 unter den Befehlen des Commodore B. von Wu¨llerstorf-Urbair Erster Band: Sporenpflanzen Botanischer Theil (Kaiserlich-Kniglichen Hof- und Staatsdruckerei, in Commission bei K. Gerold, 1870)

Reise der österreichischen Fregatte Novara um die Erde in den Jahren 1857, 1858, 1859 unter den Befehlen des Commodore B. von Wüllerstorf-Urbair - Österreichische Akademie der Wissenschaften. (Kaiserlich-Königliche Hof- und Staatsdruckerei; in Commission bei K. Gerold's Sohn, 1870)

Reise in Ostafrika in den Jahren 1903-1905 : mit Mitteln der Hermann und Elise geb. Heckmann Wentzel-Stiftung : Wissenschaftliche Ergebnisse - Voeltzkow, Alfred, 1860 -1946 (E. Schweizerbartsche Verlagsbuchhandlung, 1917)

Reisen in Britisch-Guiana in den Jahren 1840-1844 : nebst einer Fauna und Flora Guiana's nach Vorlagen von Johannes Müller, Ehrenberg, Erichson, Klotzsch, Troschel, Cabanis und Andern - Ehrenberg, Christian Gottfried, 1795 -1876 (J. J. Weber, 1847)

Reisen in Ost Afrika in 1859-61. Band III : Abteilung 3 Botanik - Decken, Karl Klaus von der, freiherr, 1833 -1865 ([s.n.], 1879)

Répertoire des noms génériques mentionnés dans l'Index kewensis et ses quinze premiers suppléments = Guide to the generic names appearing in the Index Kewensis and its fifteen supplements = Repertorio de los nombres genericos enumerados en el Index Kewensis y sus quince suplementos = Repertorium der im Index Kewensis und seinen fuenfzehn ersten Supplementen erwaehnten Gattungsnamen - Rouleau, Ernest 1916 -1991 (Châtelain, 1981)

Repertorium annuum literaturae botanicae periodicae - Bemmelen, J. A. van. (Erven Loosjes, 1873)

Repertorium specierum novarum regni vegetabilis (Selbstverlag des Herausgebers, 1908)