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 friesii Ruprecht (1845: 43) , Fig. 3 Annual, rhizome filiform, stem filiform, slightly compressed. Leaves submersed, linear, green, often with reddish or brownish tinge, 30–50 mm long, 1–2.5 mm wide, (3–)5–7-veined, margins entire, acuminate at apex; stipules not fused, connate, 7–9 mm long, fibrous, splitting into two parts when mature. Spike 7–9 mm long, peduncle 15–20 mm long, as thick as the stem. Tepals 1 mm long, anthers 0.8–0.9 mm long. Carpels 4, fruits 2 mm long. Stele of circular type , endodermis of O-type, interlacunar bundles absent, subepidermal bundles present. The species is distinguished from morphologically similar Potamogeton pusillus Linnaeus (1753: 127) by having broader, often reddish, 5–7-veined leaves and by the splitting stipules. Worldwide distribution: —Circumpolar, boreal and temperate regions throughout the northern hemisphere. Distribution in Iran :—West, Central. Flowering time: —From spring to autumn. Specimen examined :— IRAN . Gilan : Astara , Plasi village , - 84 m , 11 Aug 2014 , Dinarvand 8230 ( Herbarium of the Research Center of Agriculture & Natural Resources of Khuzestan !) ; Isfahan : Deemeh spring, 2133 m , 18 Sep 2014 , Abbasi & Afsharzadeh 19635 ( HUI !) ; Bahadoran garden ( Zarrin Shahr ), 1681 m , 26 Sep 2014 , Abbasi & Afsharzadeh 19636 ( HUI !), Chaharmal and Bakhtiari: Gandoman wetland, 2254 m , 27 Aug 2014 , Abbasi & Afsharzadeh 19637 ( HUI !), Kurdistan : Kamyaran river , 1000 m , 7 June 2015 , Abbasi & Afsharzadeh 20216 ( HUI !) .