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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.


Plant from rhizomes, occasionally with overwintering buds (late in growing season); occasionally terrestrial. Stem: simple or branched, generally green. Leaf: submersed leaves generally whorled, 3–6 per node; emergent leaves entire to pinnately divided, occasionally bract-like. Inflorescence: generally emergent, spike-like, simple or branched, terminal, flowers in whorls. Flower: proximal pistillate, middle occasionally bisexual, distal staminate; calyx lobes 4; petals generally 4, ephemeral on staminate flowers, minute or 0 on pistillate flowers; stamens generally 8; ovary 4-chambered. Fruit: mericarps 4, nut-like.
± 60 species: worldwide. (Greek: many leaves, from leaf segments) [Ceska et al. 1986 Brittonia 38:73–81] Myriophyllum specimens best collected in flower or fruit.
Unabridged note: Plants should be washed first and then "floated" on the herbarium mounting paper in a shallow dish with water [see Ceska & Ceska 1987 Ann Missouri Bot Gard 73:825–827].

Key to Myriophyllum

1. Leaves alternate, or whorled with some scattered single leaves ..... M. hippuroides

1' Leaves whorled (opposite)

2. Plants dioecious; leaves narrow, length 3–4 × width; bracts ± = stem leaves ..... M. aquaticum

2' Plants monoecious; leaves generally wider; bracts < stem leaves.

3. Bracts pinnately dissected; stems green, dark green to ± black-green when dry ..... M. verticillatum

3' Bracts entire or dentate; stems dark green, occasionally red-tinged; generally ± white to pink or dark gray when dry.

4. Leaves dark green when fresh, darker when dry, glaucous; young shoots with >= 1 pair of entire, opposite leaves at base; plants conspicuously rhizomed; flower bracts triangular, 4–10 mm, toothed, glaucous ..... M. quitense

4' Leaves dark green when fresh, generally red-tinged, not glaucous when dry, occasionally waxy from diatoms; young shoots lacking pairs of entire, opposite leaves at base; plants not conspicuously rhizomed; flower bracts lanceolate to ovate or oblanceolate, 1–3 mm, entire to toothed, not glaucous

5. Leaf segments 4–14 pairs; angles, spacing varying throughout leaf ..... M. sibiricum

5' Leaf segments 14–24 pairs; angles, spacing uniform throughout leaf ..... M. spicatum


Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, [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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