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HYDROCHARITACEAE WATERWEED FAMILY

Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes

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.
± 17 genera, ± 130 species: worldwide; some cultivated for aquaria, others noxious weeds. [Haynes 2000 FNANM 22:26–38] Ottelia alismoides (L.) Pers. is a possibly extirpated alien. —Scientific Editor: Thomas J. Rosatti.
Unabridged references: [Les, D. H. [et al. 2006], Moody, M. L., & Soros, C. L. 2006. A reappraisal of phylogenetic relationships in the monocotyledon family Hydrocharitaceae (Alismatidae). Pp. 211–230, in Columbus, J. T., Friar, E. A., Porter, J. M., Prince, L. M., & Simpson, M. G. (eds), Monocots: Comparative Biology and Evolution. Excluding Poales. Rancho Santa Ana Botanical Garden, Claremont, Ca. [Aliso 22: 211–230.]; Tanaka, N., Uehara, K., & Murata, J. 2004. Correlation between pollen morphology and pollination mechanisms in the Hydrocharitaceae. J. Plant Res. 117:265–276]

Key to Hydrocharitaceae

ELODEA
Perennial herb, rooting at nodes, submersed; dioecious or some flowers bisexual. Stem: slender, generally branched. Leaf: often 2 per node proximally, 3–7 distally, sessile, minutely serrate, midrib abaxially ± smooth. Inflorescence: axillary, sessile or not; flower 1; bract generally notched. Staminate flower: floating, deciduous or not; perianth tube elongate, slender, peduncle-like; stamens 3–9. Pistillate flower: floating; perianth tube elongate, slender, peduncle-like; style slender, stigmas 3, lobes 0 or 2. Fruit: cylindric to ovoid. Seed: several, smooth.
± 12 species: temperate, tropical America. (Greek: of marshes)
Unabridged references: [St. John, 1965 Rhodora 67:1–35, 155–180]

Key to Elodea

E. nuttallii (Planch.) H. St. John NUTTALL'S WATERWEED
NATIVE
Leaf: generally not crowded at stem tips, 3(4) per node on mid, upper stems; blade generally 6–13 mm, 0.3–2 mm wide, linear to narrowly lanceolate, acute at tip, flaccid or not. Staminate inflorescence: bract 2.2–4 mm; peduncles, flowers deciduous in bud. Staminate flower: sepals ± 2 mm, ± 1.5 mm wide; petals generally 0 or ± 0.5 mm. Pistillate flower: sepals ± 1 mm. Seed: short-soft-hairy.
2n=48. Shallow water, streams, lakes, ponds; 500–2800 m. Klamath Ranges, High Sierra Nevada, Sacramento Valley, San Bernardino Mountains, Great Basin Floristic Province; to Washington, central United States; naturalized in Europe. Jul–Aug [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Jul 26 2014
Citation for this treatment: [Author of taxon treatment] 2013. Elodea, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=24057, accessed on Jul 26 2014

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click for enlargement Elodea nuttallii
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© 2006 Dean Wm. Taylor, Ph.D.

Bioregions in which Elodea nuttallii occurs 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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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.