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POTAMOGETONACEAE PONDWEED FAMILY

C. Barre Hellquist, Robert F. Thorne & Robert R. Haynes

Annual, perennial herb, aquatic, (generally fresh to alkaline), glabrous, from rhizomes, tubers, or winter buds. Stem: erect, simple to branched, cylindric to compressed, rooting at lower nodes; nodal glands present or not. Leaf: simple, cauline, alternate or in subopposite pairs; submersed thread-like to round, sessile or petioled; floating present or not, elliptic to ovate, petioled, leathery; sheath open, continuous with petiole or ± free from blade base, generally stipuled, stipules fused and ligule-like or not. Inflorescence: spike, cylindric to spheric, axillary or terminal, generally emergent, peduncled; bracts 0. Flower: inconspicuous, bisexual; perianth parts [0]4, clawed, ± green, limb generally adaxially concave; stamens [2]4, each fused to base of perianth part [or not], filament generally 0 [short, wide], anthers open to outside; pistils [1]4, ovary 1-chambered, ovule 1, attached to chamber base, style 0 or short. Fruit: drupe, generally obovate, sessile. Seed: 1.
3 genera, ± 95 species: worldwide. [Haynes & Hellquist 2000 FNANM 22:47–74] Recently treated elsewhere to include Zannichelliaceae. Ruppia moved to Ruppiaceae. —Scientific Editor: Thomas J. Rosatti.
Unabridged references: [Angiosperm Phylogeny Group 1998 Ann Missouri Bot Gard 85:531–553]

Key to Potamogetonaceae

POTAMOGETON PONDWEED
Annual, perennial herb, rhizomed or not, tubers 0, winter buds generally 0. Stem: simple or branched, cylindric to compressed; nodal glands present or 0. Leaf: submersed, also floating or not, generally flat, generally green, entire to finely serrate; submersed sessile or not, linear to round, tip rounded to acuminate, veins 1–35; floating 0 or generally petioled, elliptic to ovate, leathery; stipules of submersed leaves free from blade base or fused to it < 1/2 stipule length. Inflorescence: generally floating to emergent; peduncle stiff. Fruit: generally beaked, abaxially with 0 or 1 central keel, 0 or 2 lateral, sometimes lower keels, sides concave to convex.
± 88 species: generally temperate northern hemisphere. (Greek: river neighbor, from aquatic habitat) Other taxa in TJM (1993) moved to Stuckenia.
Unabridged references: [Haynes 1974 Rhodora 76:564–649; Haynes 1985 Sida 11:173–188; Wiegleb 1988 Fedde Rep Sp Nov Regni Veg 99:249–266; Wiegleb & Kaplan 1998, Folia Geobot 33: 241–316.]

Key to Potamogeton

P. epihydrus Raf. NUTTALL'S RIBBON-LEAVED PONDWEED
NATIVE
Perennial herb, rhizomes slender, matted, winter buds 0. Stem: < 170 cm, branches 0–few, compressed. Leaf: submersed sessile, 5–25 cm, 2–10 mm wide, linear, ribbon-like, with a net-like band along midrib, tip acute, veins 3–13; floating generally opposite, petioled, blade 2–8 cm, 0.4–3.5 cm wide, generally oblong to elliptic, base tapered, tip rounded, veins 3–13; stipules generally < 4 cm, free from blade base, not sheathing, ligule-like. Inflorescence: 1–4 cm. Fruit: 2.5–4.5 mm, 2–3.6 mm wide, spheric to obovate, keels 3, sides concave.
n=13. Shallow water, ponds, lakes, streams; 400–1900 m. Outer North Coast Ranges, High Sierra Nevada, Modoc Plateau; to Alaska, eastern North America, Colorado. [Potamogeton epihydrus subsp. nuttallii (Cham. & Schltdl.) Calder & Roy L. Taylor] Hybridizes with Potamogeton nodosus, Potamogeton gramineus. Jul–Aug [Online Interchange] {CNPS list}

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Next taxon: Potamogeton foliosus

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Oct 25 2014
Citation for this treatment: [Author of taxon treatment] 2013. Potamogeton, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=39564, accessed on Oct 25 2014

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Geographic subdivisions indicated for the distribution of Potamogeton epihydrus Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.