7. Lemna turionifera Landolt (duckweed)

Map 388

Plants of single fronds or with 2 or 3 fronds connected by small stalks that soon wither, producing rounded, rootless, olive to brown turions (specialized, overwintering fronds) late in season. Roots 1–6(–10) cm long, the sheath at the base not winged, the tip blunt when fresh, often appearing pointed when dry. Fronds 1.5–4.0 mm long, sometimes with reddish margins, spots, or areas, flattened to slightly convex below, ovate to nearly orbicular, the bases rounded, the margins entire. Papules 2–4 per frond, all about the same size. Veins 3 per frond, sometimes difficult to see, the midvein extending nearly the entire distance from the attachment point of the roots to the tip. Fruits 1.0–1.4 mm long, the seed with 30–60 indistinct ribs. 2n=40, 42, 50, 80.

Uncommon, known from a single historical collection from Jackson County (North America south to northern Mexico, Europe, Asia). Floating on shallow water.

Landolt (1986) reported a collection from Clark County, but this could not be confirmed to date.