Synopsis of Potamogetonaceae in Iran with supplements to the Flora Iranica and a new identification key Author Abbasi, Shabnam * Department of Biology, Faculty of Science, University of Isfahan, P. O. Box 73441 - 81746, Isfahan, Iran Author Afsharzadeh, Saeed * Department of Biology, Faculty of Science, University of Isfahan, P. O. Box 73441 - 81746, Isfahan, Iran Author Dinarvand, Mehri Forests and Rangelands Research Department, Khuzestan Agricultural and Natural Resources Research and Education Center, Agricultural Research Education and Extension Organization (AREEO), Ahvaz, Iran Author Wiegleb, Gerhard Department of Ecology, BTU Cottbus-Senftenberg, Cottbus, Germany text Phytotaxa 2017 2017-06-23 311 1 1 21 http://dx.doi.org/10.11646/phytotaxa.311.1.1 journal article 10.11646/phytotaxa.311.1.1 1179-3163 13686054 Potamogeton trichoides Chamisso & Schlechtendal (1827: 175) , Fig. 5 Annual, rhizome filiform, stem filiform, terete. Leaves monomorphic; submersed leaves sessile, 14–80 mm long, 0.3–1 mm wide, gradually tapering to an acute apex, cuneate at base, 1(–3)-veined with one prominent midrib, side veins ending far before apex; floating leaves absent; stipules 3 mm long, not fused, membranaceous. Spike 1–3 mm long, peduncle 7–9 mm long; as thick as the stem. Tepals 1 mm long, anthers 1 mm long. Carpels 1, fruit 2 mm long. Stele of circular type , endoderm of O-type, interlacunar bundles absent, subepidermal bundles present. This species is distinguished from morphologically similar species P. pusillus Linnaeus (1753: 127) and P. berchtoldii Fieber (1838: 277) by the presence of only one carpel. Worldwide distribution :—Europe, N, E and S Africa, W Asia ( Turkey ), SW and C Asia. Distribution in Iran :—West. Flowering time: —Flowering in summer. Specimen examined :— IRAN . Azerbaijan : Ardebil to Khalkhal, 22 km SE of Budalalou, Neor lake, 1450 m , 20 July 2010 , Zehzad, Jamzad, Taheri & Izadpanah 70520 (TARI!).