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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
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POTAMOGETONACEAE

PONDWEED FAMILY

Robert F. Thorne

Annual, perennial herb, aquatic, (generally fresh to alkaline water), glabrous, from rhizomes or small, bulb-like, winter buds
Stems erect, simple to branched, cylindric or flattened
Leaves simple, cauline, alternate or in subopposite pairs; submersed thread-like to round, sessile or petioled; floating, if present, elliptic to ovate, petioled, leathery; sheath open, continuous with petiole or ± free from leaf base, generally with stipules, stipules sometimes fused, ligule-like
Inflorescence: spike or head-like, axillary or terminal, generally emergent, peduncled; bracts 0
Flower bisexual; perianth parts 0 or 4, clawed; stamens 2 or 4, if 4, each fused to base of perianth part, sessile or filament short, wide, anthers open to outside; pistils 4, ovary 1-chambered, ovule 1, style short or stigmas sessile
Fruit: drupe
Seed 1
Genera in family: 3 genera, ± 95 species: worldwide
Recent taxonomic note: Recently treated to include Zannichelliaceae [Angiosperm Phylogeny Group 1998 Ann Missouri Bot Gard 85:531–553].

POTAMOGETON

PONDWEED

Annual, perennial herb, from rhizomes or small, bulb-like, winter buds
Stem simple or branched, cylindric or flattened, rooting at lower nodes
Leaves simple, cauline, generally alternate, generally flat, generally green, margin generally entire; submersed leaves sessile or petioled, linear to round, tip rounded to acuminate, veins 1–35; floating leaves, if any, elliptic to ovate, generally petioled, leathery; stipules free or fused, sheath-like below leaf junction, free or fused (ligule-like) above leaf junction
Inflorescence: cylindric spike or head-like, axillary or terminal, floating to emergent
Flower: inconspicuous; perianth parts 4, clawed, greenish; stamens 4, attached to base of perianth, anthers generally sessile; ovule attached at chamber base, style short or stigma sessile
Fruit generally obovate, sessile, floating
Species in genus: ± 90 species: mostly temp n hemisphere
Etymology: (Greek: river neighbor, from aquatic habitat)
Reference: [Haynes 1974 Rhodora 76:564–649; 1985 Sida 11:173–188; Wieglet 1988 Feddes Repert 99:249–266]

Native

P. gramineus L.

GRASS-LEAVED PONDWEED

Perennial from matted rhizomes
Stem with many short branches, < 100 cm, cylindric
Leaves: submersed leaves generally sessile, 2–11 cm, 1–12 mm wide, linear to oblanceolate, tip acute or long-tapered; floating leaves generally on short, axillary branches, with petiole > blade, blade 1.5–7 cm, 1–3 cm wide, elliptic to ovate, tip ± obtuse; stipules < 3 cm, free, persistent
Inflorescence: spike, 1–4 cm
Fruit 1.5–3 mm; back faintly keeled; beak recurved
Chromosomes: n=26
Ecology: Uncommon. Shallow water, ponds, lakes, bogs
Elevation: 900–2750 m.
Bioregional distribution: Klamath Ranges, Inner North Coast Ranges, High Cascade Range, High Sierra Nevada, San Francisco Bay Area, San Bernardino Mountains, Great Basin Floristic Province
Distribution outside California: to Alaska, Greenland, Arizona, Eurasia
Flowering time: Jul–Aug
Hybridizes with P. alpinus, P. illinoensis, P. natans, P. nodosus, P. richardsonii.

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bioregional map for POTAMOGETON%20gramineus being generated
 
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Retrieve Jepson Interchange Index to Plant Names entry for Potamogeton gramineus
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