LEMNACEAE

DUCKWEED FAMILY

Wayne P. Armstrong

Perennial, floating aquatics, small, clonal, in dense populations; new plants produced in budding pouch at base or along margins; may overwinter on bottom as dense, rootless, starch-filled daughter plant (winter bud); roots 0–many
Plant body 0.4–10 mm, flat and tongue-shaped to spheric
Flower 1, rarely seen, minute, appearing like 2–3 unisexual flowers, often sheathed by minute membrane; perianth 0; stamens 1–2; pistil 1, simple, maturing before stamens
Fruit achene-like, sometimes winged
Seeds 1–3, smooth or ribbed. Spp. best separated by chemistry and fruit; clones vary; magnification, backlighting generally needed to identify vegetative plants
Genera in family: 4 genera, 34 species: worldwide; ornamental in pools, aquaria
Reference: [Landolt 1986 Veröff Geobot Inst ETH Stiftung Rübel Zürich 71]
Horticultural information: TRY.

WOLFFIELLA

MUD-MIDGET

Plants generally in unequal pairs; roots 0
Plant body 3–10 mm, thin-membranous, flat, linear to oblong, floating just below water surface; free ends generally recurved; budding pouch triangular, with track of long cells on lower surface between midline and margin; winter buds 0
Flower produced in cavity on upper surface; sheathing membrane 0; stamen 1; pistil 1
Seed smooth
Species in genus: 9 species: worldwide, especially warm temp, tropical
Etymology: (Diminutive of Wolffia)
Reference: [Landolt 1984 Veröff Geobot Inst ETH Stiftung Rübel Zürich 51:164–172]

Native

W. oblonga (Phil.) Hegelm.

Plant body not forming semicircle when viewed from side; upper surface generally flat; budding pouch with track of long cells along edge of lower wall
Ecology: Uncommon
Elevation: Habitat and range of W. lingulata.
Bioregional distribution: North Coast, Sierra Nevada Foothills, Great Central Valley, Central Coast, San Francisco Bay Area, South Coast? Daughter plant often angled from axis of parent, so pair appears boomerang-like.