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HALORAGACEAE

WATER-MILFOIL FAMILY

Elizabeth McClintock

Annual, perennial herb, shrub, generally monoecious, generally aquatic
Leaves cauline, opposite, alternate, or whorled; submersed blades with pinnate, thread-like divisions; aerial leaves simple, entire to divided
Inflorescence: panicle, raceme, or spike; flowers 1 or clustered, short-pedicelled to ± sessile
Flower generally unisexual (bisexual in Haloragis ), small, biradial; calyx tube short, fused to ovary, lobes 2–4; petals generally 2–4; stamens 4 or 8, filaments generally short; ovary inferior, chambers 1–4, styles 2–4, separate, stigmas generally plumose
Fruit fleshy or nut-like, dehiscent or not
Seeds generally 1 per chamber
Genera in family: 6–8 genera, ± 100 species: especially s hemisphere, some cultivated.

MYRIOPHYLLUM

WATER-MILFOIL

Perennial from rhizomes, sometimes with overwintering bulblets, generally monoecious
Stems simple or branched, generally open, generally green
Leaves: submersed leaves whorled, 3–6 per node, pinnate divisions thread-like; emergent leaves opposite, leaf- or bract-like, entire to pinnately divided
Inflorescence spike-like, terminal, or flowers clustered, axillary, generally emergent
Flower unisexual; lower pistillate; middle sometimes bisexual; upper staminate; calyx lobes 4; petals generally 4, ephemeral on staminate flowers, minute or 0 on pistillate flowers; stamens generally 8; ovary 4-chambered, stigma plumose
Fruit: segments 4, nut-like
Seed 1 per chamber
Species in genus: ± 40 species: worldwide
Etymology: (Greek: many leaves, from leaf divisions)
Reference: [Aiken & McNeill 1980 J Linn Soc Bot 80:213–222]

Native

M. hippuroides Torr. & A. Gray

WESTERN MILFOIL

Monoecious
Stem > 1 m
Leaves: submersed leaves > 2 cm; midrib and divisions linear, divisions < 10 mm, 14–20(40) per leaf
Inflorescence: spike, 3–12 cm, emergent; leaves 5–15 mm, 1–2 mm wide, >> flowers, generally entire to ± toothed
Ecology: Ponds, ditches, small streams
Elevation: < 1100 m.
Bioregional distribution: North Coast, Inner North Coast Ranges, n High Sierra Nevada, San Joaquin Valley
Distribution outside California: to Washington, eastern US
Horticultural information: TRY.

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