Myriophyllum aquaticum |
Myriophyllum hippuroides |
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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 |
western milfoil, western water-milfoil |
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Habit | Herbs dioecious, pistillate, not staminate, in flora area, aquatic or semiaquatic, often forming dense stands. | Herbs monoecious, aquatic, sometimes forming dense stands. |
Stems | branched or unbranched, to 5 m. Turions absent. |
often branched, to 1.5 m. Turions absent. |
Leaves | 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. |
usually in whorls of 4(–6), sometimes subverticillate, heteromorphic; petiole to 3 mm; submersed leaves pectinate, obovate in outline, (12–)16–30(–41) × (10) 12–22(–30) mm, segments 12–24, linear-filiform, longest segment (6–)9–25(–36) mm; emersed leaves pectinate to pinnatifid proximally, linear to narrowly oblong or linear-lanceolate distally, (5–)7–16(–23) × (0.5–)1–2.2(–2.6) mm, often increasing in size distally, segments (5–)10–16(–22), 0–2.5 mm, margins serrate to shallowly lobed. |
Inflorescences | 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. |
to 35 cm; flowers proximally pistillate, medially bisexual, distally staminate; bracteoles cream, ovate to triangular, (0.4–)0.7–1 × 0.2–0.7 mm, margins irregularly lobed. |
Staminate flowers | 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, trullate to lanceolate, (0.1–)0.2–0.4(–0.5) × 0.1–0.4(–0.5) mm; petals persistent, cream to pink, elliptic to ovate, 1–1.5 ×0.5–0.8(–0.9) mm; stamens 4, filaments to 1 mm, anthers 0.5–0.9 × 0.2–0.4 mm. |
Pistillate flowers | 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. |
sepals cream, trullate to lanceolate, 0.2–0.4 × 0.1–0.2 mm; petals persistent, cream to pink, elliptic to ovate, 0.7–1.3 × 0.4–0.7 mm; pistils 1.1–1.5 mm, stigmas red to ± purple, to 0.4 mm. |
Fruits | cylindric to ovoid, shallowly 4-lobed. |
cylindric to subglobose, cruciate to deeply 4-lobed. |
Mericarps | olive-green to brown, cylindric, 1.7 × 0.6–0.7 mm, narrowly obovate, abaxial surface rounded, ridges, wings and ribs absent. |
tan to light green to red-brown or purple, cylindric to narrowly ovoid, 1.1–1.5 × 0.4–0.6 mm, transversely elliptic to narrowly ovate, compressed to flattened, abaxial surface bluntly 2-angled, flattened to slightly rounded, papillate to tuberculate, with 2(or 4) shallow, longitudinal ridges, wings and ribs absent. |
Myriophyllum aquaticum |
Myriophyllum hippuroides |
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Phenology | Flowering and fruiting Apr–Sep. | Flowering and fruiting late Apr–Nov. |
Habitat | Lakes, canals, bays, ponds, slow moving ditches, creeks, rivers. | Oligotrophic to mesotrophic waters, lakes, ponds, pools, riparian sloughs, small streams. |
Elevation | 0–1500 m. (0–4900 ft.) | 0–1800 m. (0–5900 ft.) |
Distribution |
AL; AR; AZ; CA; CT; DC; DE; FL; GA; ID; IL; IN; KS; KY; LA; MA; MD; MN; MO; MS; NC; NJ; NM; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; WA; WI; WV; BC; South America [Introduced in North America; introduced also in Mexico, Central America, Eurasia, Africa, Indian Ocean Islands, Pacific Islands, Australia]
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CA; IL; OR; WA; BC; Mexico; Central America
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Discussion | 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.) |
Myriophyllum hippuroides has a disjunct range in North America. It is native to the Pacific Northwest and California, where it can be confused with M. pinnatum and M. heterophyllum (see 12. M. pinnatum). Myriophyllum hippuroides often produces a terrestrial form consisting primarily of emergent leaves. The linear-lanceolate emergent leaves of M. hippuroides are at least three times as long as broad compared to the elliptic to ovate emergent leaves of M. heterophyllum. The most distinctive difference between these species is the morphology of their mericarps. The relatively narrow, transversely elliptic mericarps of M. hippuroides have a sharply 2-angled abaxial surface and are distinctly different from the subglobose and inconspicuously 4-angled mericarps of M. heterophyllum and the widely winged and ribbed mericarps of M. pinnatum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 10. | FNA vol. 10. |
Parent taxa | Haloragaceae > Myriophyllum | Haloragaceae > Myriophyllum |
Sibling taxa | ||
Synonyms | Enydria aquatica, M. brasiliense, M. proserpinacoides | |
Name authority | (Vellozo) Verdcourt: Kew Bull. 28: 36. (1973) | Nuttall ex Torrey & A. Gray: Fl. N. Amer. 1: 530. (1840) |
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