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Najas gracillima
THREAD-LEAVED WATER-NYMPH

Higher Taxonomy
Family: HydrocharitaceaeView DescriptionDichotomous Key

Common Name: WATERWEED FAMILY
Habit: Annual, perennial herb, aquatic, freshwater or marine, glabrous or hairy; monoecious, dioecious, or flowers bisexual. Leaf: basal, alternate, opposite, or whorled, generally sessile, generally +- sheathing at base. Inflorescence: axillary, terminal, or scapose, cyme or flowers 1, subtended by +- sheathing, entire or lobed bract; staminate flowers sometimes deciduous, free-floating. Flower: generally radial; perianth 0 or tube 0 or elongate, peduncle-like in flower; sepals (0)3(4), green; petals (0)3(4), white or not; stamens (0)2--many, generally in 1+ series; ovary inferior, chamber 1 or falsely 6--9, placentas parietal, 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. Note: Ottelia alismoides (L.) Pers. is a possibly extirpated alien.
eFlora Treatment Author: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes
Scientific Editor: Thomas J. Rosatti.
Genus: NajasView DescriptionDichotomous Key

Habit: Annual, aquatic, submersed, mat-like or not; monoecious or dioecious. Stem: several, often much-branched, slender. Leaf: simple, cauline, +- opposite to +- whorled, sessile; sheath generally wider than, expanded abruptly at junction with blade; blade generally linear, margin entire to coarsely spine-toothed. Inflorescence: axillary; flowers 1--few, clustered, inconspicuous. Staminate Flower: subtended by (0)2 minute involucres, inner membranous, flask-shaped, outer cup-like, tubular, or with free scales; perianth 0; stamen 1, anther opening irregularly, subsessile. Pistillate Flower: generally not subtended by involucres; perianth 0; ovary 1, chamber 1, ovule 1, style short, generally terminal (from center of ovary, fruit top), stigma 2--4-lobed. Fruit: achene-like, fusiform; outer wall thin, +- translucent.
Species In Genus: +- 50 species: +- worldwide. Etymology: (Greek: water nymph) Note: Najas graminea Delile is an agricultural weed.

Najas gracillima (Engelm.) Magnus
NATURALIZED
Habit: Monoecious. Stem: internodes not prickled. Leaf: margin teeth 13--17 per side, tip acute, with 2--3 teeth; sheath tip truncate. Staminate Flower: 1.5--2 mm; anther chambers 1. Pistillate Flower: 0.5--2.7 mm; style subterminal, stigma 2-lobed. Seed: 0.4--0.7 mm, fusiform, coat pitted, dull. Chromosomes: 2n=24,36.
Ecology: Rivers, lakes; Elevation: +- 100 m. Bioregional Distribution: n ScV, expected elsewhere; Distribution Outside California: native to northeastern United States; Eurasia. Flowering Time: Jun--Aug
eFlora Treatment Author: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes
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Citation for this treatment: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes 2016. Najas gracillima, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=34352, accessed on May 03, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on May 03, 2016.


Geographic subdivisions for Najas gracillima:
n ScV, expected elsewhere;
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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Data provided by the participants of the Consortium of California Herbaria.
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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.