2. Lemna minor L. (lesser duckweed,
common duckweed)
Pl.
97 a–d; Map 383
Plants of single fronds or with 2 or 3 fronds connected by small stalks that soon
wither, not producing turions. Roots 1–6(–10) cm long, the sheath at the base
not winged, the tip blunt when fresh, often appearing pointed when dry. Fronds
2–8 mm long, often with reddish margins, spots, or areas, flattened, narrowly
ovate to nearly orbicular, the bases rounded, the margins entire. Papules
usually 2–5 per frond, all relatively small. Veins 3(–5) per frond, sometimes
difficult to see, the midvein extending nearly the entire distance from the
attachment point of the roots to the tip. Fruits 0.8–1.0 mm long, the seed with
10–16 ribs. 2n=20, 40, 50, 63, 126.
Relatively common nearly throughout Missouri (Canada, U.S., Europe, Asia,
Africa, Australia, New Zealand). Floating on shallow, stagnant water of ponds,
lakes, sloughs, ditches, swamps, and marshes, often forming mats; also in still
backwaters and margins of spring branches, streams, and rivers, sometimes
stranded on mud by receding waterline. This is the most common species of
Lemnaceae in the state.