1. Family: Araceae Juss.
    1. Pistia L.

      1. This genus is accepted, and its native range is Tropics & Subtropics.

    [CATE]

    CATE Araceae, 17 Dec 2011. araceae.e-monocot.org

    Diagnostic
    Free-floating aquatics with pendent feathery roots; leaves rosulate, hairy; leaf blade oblong to wedge-shaped, lacking midrib, primary veins parallel, fine venation reticulate; female zone composed of a single gynoecium; male zone a single whorl of 2-8 flowers; flowers unisexual, perigone absent; male flower a synandrium of two connate stamens.
    General Description
    Laticifers absent. HABIT : small, free-floating evergreen herbs with pendent feathery roots, stem very short, acaulescent, stoloniferous. LEAVES : several in a rosette, densely pubescent. PETIOLE : very short, almost absent, sheath very short, ligulate, very thin, scarious at base. BLADE : somewhat spongy, obovate-cuneate to obovate-oblong, apically rounded, truncate or retuse; midrib absent, primary veins subparallel, all arising from base, diverging towards apex, running into margin near apex, strongly prominent on lower surface, higher order venation reticulate. INFLORESCENCE : solitary, very small, much shorter than leaves. PEDUNCLE : very short, pubescent. SPATHE : pubescent without, glabrous within, somewhat constricted centrally, lower margins connate with each other and with ovary wall forming tube, free margins between tube and blade folded between stigma and male organs forming a partition between an upper male chamber and a lower female one, blade erect, ovate, expanded, acute-acuminate. SPADIX : shorter than spathe, mostly adnate to spathe, only the apical male zone free, female zone bearing single gynoecium at base and a thin, green, pouch-shaped flap just below spathe partition, male zone subtended by a thin, marginally lobed, green, annular flap, composed of a basally naked spadix axis supporting a single whorl of 2-8 flowers, axis sometimes extending a little beyond. FLOWERS : unisexual, perigone absent. MALE FLOWER : synandrium composed of 2 connate stamens, thecae dehiscing by single apical slit. POLLEN : inaperturate, ellipsoid-elongate to -oblong, medium-sized (mean 27 µm.), exine plicate with strongly undulate frills running the length of the grain. FEMALE FLOWER : gynoecium obliquely adnate to spadix axis, ovary ovoid, 1-locular, ovules numerous, orthotropous, placenta broad, apparently parietal, probably morphologically basal, style attenuate, bending inwards towards male flowers, stigma small, discoid-subcapitate. BERRY : thin-walled, utricular, several-seeded, ellipsoid, irregularly breaking up and decaying to release seeds. SEED : barrel-shaped, ± subtruncate and excavated at apex and base, testa thick, reticulate-alveolate, thicker and with operculum at micropylar end, embryo obovoid to conoid, endosperm copious. Herbs, small, free-floating, evergreen, stoloniferous, acaulescent, with spreading feathery roots. Leaves several in a rosette, densely pubescent; petiole very short, almost absent; sheath ligulate, very short, very thin, scarious at base; leaf blade obovate-cuneate to obovate-oblong, somewhat spongy, apex rounded, truncate, or retuse; midrib absent, primary veins subparallel, all arising from base, diverging slightly and running into margin near apex, strongly prominent abaxially, higher order venation reticulate. Inflorescence solitary, very small, much shorter than leaves; peduncle very short, pubescent. Spathe somewhat constricted centrally, pubescent outside, glabrous inside, proximal margins connate with each other and with ovary wall forming tube, free margins between tube and blade folded between stigma and male organs forming a partition between a distal male partial chamber and a proximal female one; limb erect, ovate, expanded, acute-acuminate. Spadix shorter than spathe, mostly adnate to spathe, only apical male zone free; female zone with single gynoecium at base and a thin, green, pouch-shaped flap just below spathe partition; male zone subtended by a thin, marginally lobed, green, annular flap, consisting of a basally naked spadix axis supporting a single whorl of 2–8 flowers, naked axis sometimes extending slightly beyond. Flowers unisexual, naked. Gynoecium obliquely adnate to spadix axis; ovary ovoid, 1-loculed; ovules numerous, orthotropous; placenta broad, apparently parietal, probably morphologically basal; stylar region attenuate, bending inward toward male flowers; stigma disciform-subcapitate, small. Male flower a synandrium consisting of 2 connate stamens; thecae dehiscing by single apical slit. Fruit a thin-walled, utricular, several-seeded, ellipsoid berry, irregularly breaking up and decaying to release seeds. Seed barrel-shaped, ± subtruncate and excavated at apex and base; testa thick, reticulate-alveolate, thicker and with operculum at micropylar end; embryo obovoid to conic; endosperm copious.
    Distribution
    Trop. & Subtrop.
    Habitat
    Tropical wetlands; floating aquatic in open, tranquil, freshwater habitats.
    [FTEA]

    Araceae, S.J. Mayo. Flora of Tropical East Africa. 1985

    Habit
    Small, free-floating, acaulescent, rosulate, perennial, freshwater, aquatic herbs with pendent fibrous roots
    Leaves
    Leaves densely pubescent, subsessile; blade very variable in size and shape; primary veins parallel
    Inflorescences
    Inflorescence small, hidden among leaf-bases Spathe constricted centrally, basal part slightly inflated, convolute, apical part ± erect, expanded, acute-acuminate Spadix highly reduced, adnate to spathe
    Flowers
    Flowers unisexual, lacking perigon Pistillate flower solitary, basal, consisting of a single, oblique, unilocular ovary; ovules numerous on single basal placenta, style slender, curved; stigma subspherical Staminate flowers 2–8, connate into a single whorl borne on a short stipe subtended by shallow basal cup, each flower a synandrium of 2 connate stamens
    Male
    Staminate flowers 2–8, connate into a single whorl borne on a short stipe subtended by shallow basal cup, each flower a synandrium of 2 connate stamens
    Female
    Pistillate flower solitary, basal, consisting of a single, oblique, unilocular ovary; ovules numerous on single basal placenta, style slender, curved; stigma subspherical
    Fruits
    Fruit a thin-walled several-seeded berry, dehiscing by irregular splits
    Seeds
    Seeds subcylindric, rugose, with abundant endosperm.

    Images

    Distribution

    Native to:

    Afghanistan, Andaman Is., Angola, Argentina Northeast, Assam, Bangladesh, Belize, Benin, Bolivia, Borneo, Botswana, Brazil North, Brazil Northeast, Brazil South, Brazil Southeast, Brazil West-Central, Burkina, Burundi, Cabinda, Cambodia, Cameroon, Cape Provinces, Caprivi Strip, Central African Repu, Chad, China South-Central, China Southeast, Colombia, Comoros, Congo, Costa Rica, Cuba, Dominican Republic, East Himalaya, Ecuador, Egypt, El Salvador, Equatorial Guinea, Ethiopia, Florida, Free State, French Guiana, Gabon, Galápagos, Gambia, Ghana, Guatemala, Guinea, Guinea-Bissau, Gulf of Guinea Is., Guyana, Hainan, Haiti, Honduras, India, Ivory Coast, Jamaica, Jawa, Kenya, KwaZulu-Natal, Laccadive Is., Laos, Leeward Is., Lesotho, Liberia, Louisiana, Madagascar, Malawi, Malaya, Maldives, Mali, Maluku, Mauritania, Mauritius, Mexican Pacific Is., Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Northwest, Mexico Southeast, Mexico Southwest, Mississippi, Mozambique, Myanmar, Namibia, Nansei-shoto, Nepal, Netherlands Antilles, New Guinea, Nicaragua, Nicobar Is., Niger, Nigeria, Northern Provinces, Northern Territory, Pakistan, Panamá, Paraguay, Peru, Philippines, Puerto Rico, Queensland, Rwanda, Senegal, Sierra Leone, Somalia, South China Sea, Sri Lanka, Sudan, Sulawesi, Suriname, Swaziland, Taiwan, Tanzania, Texas, Thailand, Togo, Trinidad-Tobago, Uganda, Uruguay, Venezuela, Venezuelan Antilles, Vietnam, West Himalaya, Windward Is., Zambia, Zaïre, Zimbabwe

    Introduced into:

    Alabama, Aruba, Bermuda, Canary Is., Colorado, Hawaii, Illinois, Italy, Japan, Kazakhstan, Netherlands, New Caledonia, Palestine, St.Helena, Ukraine

    Pistia L. appears in other Kew resources:

    First published in Sp. Pl.: 963 (1753)

    Accepted by

    • Dobignard, D. & Chatelain, C. (2010). Index synonymique de la flore d'Afrique du nord 1: 1-455. Éditions des conservatoire et jardin botaniques, Genève.
    • Govaerts, R. & Frodin, D.G. (2002). World Checklist and Bibliography of Araceae (and Acoraceae): 1-560. The Board of Trustees of the Royal Botanic Gardens, Kew.

    Literature

    Flora of West Tropical Africa
    • F.T.A. 8: 140.
    • Sp. Pl. 963 (1753)
    Flora of Tropical East Africa
    • Engl. in E.P. 73 (IV. 23F): 258 (1920)
    • L., Gen. Pl., ed. 5: 411 (1754)
    • Sp. Pl: 963 (1753)

    Sources

    CATE Araceae
    Haigh, A., Clark, B., Reynolds, L., Mayo, S.J., Croat, T.B., Lay, L., Boyce, P.C., Mora, M., Bogner, J., Sellaro, M., Wong, S.Y., Kostelac, C., Grayum, M.H., Keating, R.C., Ruckert, G., Naylor, M.F. and Hay, A., CATE Araceae, 17 Dec 2011.
    http://creativecommons.org/licenses/by-nc-sa/3.0

    Flora of Tropical East Africa
    Flora of Tropical East Africa
    http://creativecommons.org/licenses/by-nc-sa/3.0

    Kew Backbone Distributions
    The International Plant Names Index and World Checklist of Selected Plant Families 2019. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
    © Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

    Kew Names and Taxonomic Backbone
    The International Plant Names Index and World Checklist of Selected Plant Families 2019. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
    © Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0