Jepson Flora Project: Jepson Interchange    

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

WATERWEED FAMILY

Robert F. Thorne

Annual, perennial herb, aquatic, freshwater or marine, bisexual, monoecious, or dioecious
Leaves basal or cauline, alternate, opposite, or whorled, generally ± sheathing at base, glabrous
Inflorescence: cyme; flowers 1–few, subtended by ± sheathing, entire or lobed bract; staminate flowers sometimes deciduous, free-floating
Flower radial; perianth tube 0 or much elongated, peduncle-like in flower; sepals (0)3, green; petals (0)3, colored or white; stamens (1)3–many, generally in 1+ series; ovary inferior, chamber 1, placentas parietal or basal, ovules 1–many; style lobes generally 3, linear, lobed or notched
Fruit: achene or berry-like and dehiscing irregularly, linear to spheric, submersed
Genera in family: ± 17 genera, ± 130 species: worldwide; some cultivated for aquaria, others noxious weeds.

NAJAS

Annual, aquatic, submersed, sometimes mat-like, monoecious or dioecious
Stems several, much-branched, slender
Leaves simple, cauline, opposite or appearing ± whorled; sheath generally wider than blade, expanded abruptly at junction with blade; blade generally linear, margin entire to spiny
Inflorescence axillary; flowers 1–few, clustered, inconspicuous
Staminate flower: perianth 0; stamen 1, anther opening irregularly, subsessile, subtended by 2 minute involucres, inner membranous, flask-shaped, outer cup-like, tubular, or with free scales
Pistillate flower: perianth part 0–1; ovary 1, chamber 1, ovule 1, style short, stigmas 2–4, linear
Fruit: achene, fusiform; outer wall thin, ± translucent
Species in genus: ± 50 species: ± worldwide
Etymology: (Greek: water nymph)
Reference: [Shaffer-Fehre 1991 Bot J Linn Soc 107:189–209]

Introduced

N. graminea Delile

RICE-FIELD WATER-NYMPH

Monoecious
Stem 0.5–6 dm; lateral branches short
Leaves 1–2.5 cm, 0.5–1 mm wide, tufted on lateral branches; tip recurved; sheath appendaged, appendages 2, ± = 1/2 sheath length, acuminate, minutely spine-tipped; blade margin entire, tip with 1–several minute spines
Staminate flower < 2 mm; anther 4-chambered
Pistillate flower 1.5–3 mm; stigmas 2–3
Fruit: surface dull, clearly net-like
Ecology: Very uncommon. Irrigation ditches, rice fields
Elevation: < 150 m.
Bioregional distribution: Sacramento Valley (Butte, Colusa cos.)
Distribution outside California: native to tropical Asia

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bioregional map for NAJAS%20graminea being generated
 
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Retrieve Jepson Interchange Index to Plant Names entry for Najas graminea
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Overlay Consortium of California Herbaria specimen data by county on this map
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