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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

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

1. Plants floating (rooted in mud when stranded); leaves (when floating) with swollen spongy cells abaxially ..... LIMNOBIUM

1' Plants submersed to emergent; leaves without swollen spongy cells abaxially

2. Leaves basal, petioled, alternate, lower, submersed blades elliptic to ovate, upper, floating or emergent blades ovate to cordate or reniform — flower bisexual, emergent ..... [OTTELIA]

2' Leaves cauline, sessile, opposite to whorled, blade oblong or linear

3. Perianth 0; leaves ± opposite to ± whorled; seeds smooth or pitted ..... NAJAS

3' Perianth present; leaves opposite or generally whorled; seeds smooth

4. Leaves 1.2–4 cm, 2–5 mm wide; staminate flowers 2–3, petals 8–10 mm ..... EGERIA

4' Leaves < 1.5(2) cm, < 3 mm wide; staminate flowers 1, petals generally <= 5 mm

5. Leaves often 2 per node proximally, 3–7 distally, minutely serrate, midrib abaxially ± smooth ..... ELODEA

5' Leaves generally 4–8 per node, coarsely serrate, midrib abaxially prickled or not ..... HYDRILLA

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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