Myriophyllum aquaticum
Brazilian water-milfoil, parrot feather, parrot feather watermilfoil, parrot's feather, parrot's-feather water-milfoil, parrot- or water-feather, South American water milfoil, water feather
branched or unbranched, to 5 m.
absent.
in whorls of 4–6(–8), homomorphic;
petiole to 9.6 mm; submersed leaves pectinate, oblanceolate to obovate in outline, (20–)25–70(–75) × (4–)5–26(–32) mm, segments (14–)16–36(–40), filiform, longest segment (2–)4–27(–33) mm; emersed leaves becoming unmodified floral bracts.
to 20 cm;
flowers unisexual;
bracteoles cream to stramineous, (0.3–)0.5–1(–1.5) × 0.1–0.3(–0.5) mm, margins subulate to 3-fid.
sepals cream, ovate to deltate, 0.7–0.8 ×0.3 mm;
petals yellow, weakly cucullate, (2.3–)2.7–3.1 × 0.8–1.1 mm;
stamens 8, filaments to 1.2 mm, anthers yellow, linear-oblong, (1.8–)2–2.7 × 0.2 mm.
sepals cream, lanceolate to deltate, 0.3–0.5 × 0.1–0.2(–0.4) mm;
petals rudimentary or absent;
pistils to 0.8 mm, stigmas white, to 0.3 mm.
cylindric to ovoid, shallowly 4-lobed.
olive-green to brown, cylindric, 1.7 × 0.6–0.7 mm, narrowly obovate, abaxial surface rounded, ridges, wings and ribs absent.
Myriophyllum aquaticum
In the flora area, Myriophyllum aquaticum is an introduced invasive aquatic species, existing as pistillate populations throughout North America (R. Couch and E. Nelson 1992); it is native to the lowlands of South America (A. E. Orchard 1981). It has an unusual habit among North American species of Myriophyllum, where it is often observed as a robust emergent aquatic along shorelines. It can be found also growing to a depth of 5 m in lakes, with the largest submersed leaves recorded for any North American species of Myriophyllum. The leaves of M. aquaticum are very distinctive, being largely oblanceolate and two to three times as long as broad, with a large number of uniform, short-pinnate segments, often arranged in whorls of six or more.
Myriophyllum aquaticum has been reported from Iowa and Montana; no specimens have been seen that confirm these reports.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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