Jepson Herbarium
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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

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 n 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.]

Perennial, rhizome stout.
Stem: generally < 30 cm, branches few, often zigzag, subcylindric, ± white.
Leaf: submersed, sessile, 5–20 cm, 10–30 mm wide, lance- linear, often wavy, base generally lobed, clasping, tip hood-like, splitting when dry, veins 11–33; stipules 2–10 cm, free, ± white, persistent.
Inflorescence: 3–7.5 mm; peduncle 10–30 cm.
Fruit: 4–5 mm, keels 1(3).
2n=52. Deep water, lakes; 1800–3000 m. High Cascade Range, n&c High Sierra Nevada;

Previous taxon: Potamogeton nodosus
Next taxon: Potamogeton pusillus

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].

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Bioregions in which taxon occurs	Red area (if present) is the part of the bioregion lying between the upper and lower elevation limits of the taxon; 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 have georeferencing or identification issues.
Chart based on elevation range in Manual and elevations and coordinates of CCH records. Data provided by the participants of the Consortium of California Herbaria. Note: About half of the CCH records include both elevation and coordinates.	Map made in collaboration with Scott Loarie. Data provided by the participants of the Consortium of California Herbaria. View all CCH records   CCH collections by month Duplicates counted once; synonyms included. Species do not include records of infraspecific taxa. Blue line denotes Manual flowering time.