Myriophyllum quitense
Myriophyllum humile
Andean water-milfoil, waterwort milfoil, waterwort water-milfoil
low water-milfoil, myriophylle menu, western water-milfoil
often branched, to 3 m. Turions absent.
often branched, to 1 m. Turions absent.
mostly in whorls of (3 or)4(or 5), sometimes opposite to subopposite, heteromorphic;
petiole 0–4 mm; submersed leaves pectinate to lobed (basalmost leaves opposite to subopposite, reduced, margins entire), ovate to obovate in outline, (3–)5–25(–35) × (2–)3–18(–20) mm, segments (2 or)3–9(–11), linear, ± applanate, longest segment (7–)8–15(–17) mm; emersed leaves pinnatisect to lobed or entire, ovate to oblong in outline, 2–9 × 1–6 mm, margins dentate to minutely serrate.
usually alternate or opposite, rarely in whorls of 3(or 4), heteromorphic;
petiole to 4 mm; submersed leaves pectinate, ovate to elliptic in outline, (5.5–)10–27(–30) × (4.4–)6–22(–33) mm, segments (2–)4–13(–14), linear-filiform, longest segment (3–)8–17(–22.5) mm; emersed leaves usually pectinate to pinnatifid proximally, linear to spatulate or lobed distally, 5–9(–12.5) × 0.3–3(–6) mm, segments (0–)4–6(–9).
to 8 cm;
flowers proximally pistillate, medially bisexual, distally staminate;
bracteoles cream, deltate, 0.5–1 × 0.2–0.6 mm, margins dentate to serrate, with glandular tip.
to 35 cm, sometimes submersed with flowers in axils of unmodified, pectinate leaves;
flowers proximally pistillate, distally staminate;
bracteoles cream, oblong to elliptic to ovate or triangular, 0.3–0.7 × 0.1–0.4 mm, margins entire or irregularly lobed, apex often aristate.
sepals green to cream, ovate to deltate, (0.2–)0.3–0.5(–0.7) × (0.1–)0.2–0.4(–0.5) mm;
petals persistent, ± purple, oblong, 2–3 × 0.5–1.5 mm;
stamens 8, filaments to 0.6 mm, anthers 1.8–2.5 × 0.2–0.6 mm.
sepals cream to stramineous, triangular, 0.1–0.2 × 0.1–0.2 mm;
petals caducous, purple, elliptic to obovate, 0.6–1.5 × 0.3–0.7 mm;
stamens 4, filaments to 0.9 mm, anthers 0.3–0.8 × 0.1–0.3 mm.
sepals cream, deltate, 0.2–0.5 × 0.1–0.4 mm;
petals ± persistent, cream, ± cucullate, elliptic, 0.1–0.5 × 0.2–0.3 mm;
pistils 1.1–2.2 mm, stigmas cream to ± purple, to 0.6 mm.
sepals cream to stramineous, triangular, 0.1–0.2 × 0.1 mm;
petals caducous, purple, elliptic to obovate, 0.3–0.5 × 0.2–0.3 mm;
pistils 0.7–0.9 mm, stigmas red to ± purple, to 0.2 mm.
cylindric to oblong, 4-lobed.
cylindric, deeply 4-lobed.
tan to olive-brown, cylindric to ovoid, 1.5–1.8 × 0.6–0.8 mm, transversely elliptic, abaxial surface rounded, smooth, sometimes with a shallow, longitudinal ridge, wings and ribs absent.
tan to red-brown or purple, cylindric to narrowly ovoid, (0.6–)0.8–1.2 × 0.4–0.6 mm, transversely elliptic to ovate, abaxial surface rounded, sparsely to densely tuberculate, tubercles relatively small, shallow, wings and ridges absent.
= 42.
Myriophyllum quitense
Myriophyllum humile
The most distinguishing feature of Myriophyllum quitense is the production of relatively large, ovate distal floral bracts with serrate margins. This characteristic is shared only with M. heterophyllum; however, M. quitense has eight stamens and the latter has four.
The proximal submersed leaves of most Myriophyllum species are uniformly pectinate, but those of M. quitense can range from entire or lobed to pectinate. This species often exhibits a pronounced transition from three or four proximal nodes of large, opposite, spatulate or lobed prophylls, to nodes of besomiform whorled leaves having obtriangular laminar surfaces and distal pinnatifid segments resembling those of pectinate leaves. In addition, the unusual grayish blue color of the foliage and whitish rhizomes are useful characteristics for distinguishing submersed vegetative specimens of M. quitense from similar species, such as M. sibiricum.
Myriophyllum quitense has a highly disjunct distribution in North America and South America (A. E. Orchard 1981; O. Ceska et al. 1986). S. G. Aiken (1981) and R. Couch and E. Nelson (1988) suggested that M. quitense was introduced into North America by migratory waterfowl. Both Ceska et al. and M. L. Moody and D. H. Les (2010) regarded it as native to North America. It has been reported from New Brunswick and Prince Edward Island (D. F. McAlpine et al. 2007) and further range extensions would seem likely given the level of disjunction in distribution.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Myriophyllum humile has a diminutive semiterrestrial growth form, referred to as var. limosum by T. Morong (1891), that has alternate and, typically, spatulate floral bracts that can be confused with the emergent form of M. pinnatum. In vegetative form, the leaves of M. pinnatum tend to be pectinate with a greater number of longer segments than those of M. humile, which are often linear, spatulate, or 4–6-lobed. When fruits are present, the two can be distinguished by the presence of winged ridges on the mericarps in M. pinnatum, which are absent in M. humile. Submersed forms of M. humile can be confused with M. farwellii because of the delicate nature of their leaves. M. humile has leaves mostly alternate and opposite; leaves in M. farwellii tend to be whorled or, sometimes, subverticillate, giving these plants a bushy appearance. Myriophyllum humile can be also confused with M. laxum (see 10. M. laxum discussion).
All specimens examined from Minnesota labeled Myriophyllum humile have been misidentified and are other species of the genus. Only one sterile herbarium specimen labeled as M. humile from Wisconsin has been seen, but its identity could not be confirmed.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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