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Potamogeton illinoensis
SHINING PONDWEED

Higher Taxonomy
Family: PotamogetonaceaeView DescriptionDichotomous Key

Common Name: PONDWEED FAMILY
Habit: 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.
Genera In Family: 3 genera, +- 95 species: worldwide. Note: Recently treated elsewhere to include Zannichelliaceae. Ruppia moved to Ruppiaceae.
eFlora Treatment Author: C. Barre Hellquist, Robert F. Thorne & Robert R. Haynes
Scientific Editor: Thomas J. Rosatti.
Genus: PotamogetonView DescriptionDichotomous Key

Common Name: PONDWEED
Habit: 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.
Species In Genus: +- 88 species: generally temperate northern hemisphere. Etymology: (Greek: river neighbor, from aquatic habitat) Note: Other taxa in TJM (1993) moved to Stuckenia.

Potamogeton illinoensis Morong
NATIVE
Habit: Perennial herb, rhizomed. Stem: < 150 cm, branches generally many, slender, cylindric. Leaf: submersed blade 6--20 cm, 15--50 mm wide, elliptic to oblanceolate, microscopically serrate near tip, tip acute-mucronate, veins 7--19, petiole 0 or 0.5--4 cm; floating 0 or blade generally > petiole, 4--12 cm, 2--6 cm wide, widely elliptic to oblong-elliptic, tip rounded-mucronate, veins 13--29; stipules 2.5--7 cm, free, persistent. Inflorescence: generally < 6 cm. Fruit: 2.5--3.6 mm, keels 3, lateral lower, beak erect to +- recurved, 0.5--0.8 mm. Chromosomes: n=52.
Ecology: Lakes, ponds, streams; Elevation: 400--2350 m. Bioregional Distribution: NCoR, CaR, SNH, GV, CW (exc SCoRI), SnGb, SnBr, PR, GB; Distribution Outside California: to British Columbia, eastern Canada, Texas, Baja California; also Central America, South America, Caribbean. Flowering Time: Jun--Aug Note: Hybridizes with Potamogeton amplifolius, Potamogeton gramineus, Potamogeton nodosus, Potamogeton richardsonii.
eFlora Treatment Author: C. Barre Hellquist, Robert F. Thorne & Robert R. Haynes
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Next taxon: Potamogeton natans

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Citation for this treatment: C. Barre Hellquist, Robert F. Thorne & Robert R. Haynes 2016. Potamogeton illinoensis, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=39581, accessed on August 31, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on August 31, 2016.


Potamogeton illinoensis
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© 2008 Neal Kramer

More photos of Potamogeton illinoensis in CalPhotos


Geographic subdivisions for Potamogeton illinoensis:
NCoR, CaR, SNH, GV, CW (exc SCoRI), SnGb, SnBr, PR, GB;
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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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.