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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].

RUPPIA

DITCH-GRASS

Perennial from slender rhizomes
Stems generally many-branched, thread-like, rooting at lower nodes
Leaves cauline, alternate, < 10 cm, < 1 mm wide; tip acute; stipules < 15 mm, ± completely fused to leaf base, sheath-like below leaf junction, ± open
Inflorescence terminal; flowers 2, sessile; peduncle elongated, straight or coiled in fruit
Flower minute; perianth 0; stamens 2, anthers sessile; pistils generally 4(2–8), simple, ovule attached at top of chamber, stigma sessile, peltate
Fruit ovoid, oblique, long-stalked
Species in genus: 2+ species: temp worldwide
Etymology: (Heinrich Bernhard Ruppius, German botanist, 1688–1719)
Reference: [Setchell 1946 Proc Calif Acad Sci 25:469–478]
Recent taxonomic note: Ruppia sometimes treated in Ruppiaceae.

Native

R. cirrhosa (Petagna) Grande


Leaf < 1 mm wide; tip acute
Inflorescence: peduncle in fruit 3–30 cm, coiled or flexible
Chromosomes: 2n=40
Ecology: Marshes, ponds, sloughs
Elevation: < 2045 m.
Bioregional distribution: North Coast, Inner North Coast Ranges, Tehachapi Mountain Area, San Joaquin Valley, Central Western California, South Coast, San Bernardino Mountains, Great Basin Floristic Province, Desert
Distribution outside California: ± worldwide
Flowering time: Mar–Aug
Synonyms: R. spiralis Dumort
Possibly indistinct from R. maritima ; needs further study.

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bioregional map for RUPPIA%20cirrhosa being generated
 


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