Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
Lemnaceae - The Duckweed Family
Small or minute thalloid plants with bodies not differentiated into stems and
leaves, free-floating on or beneath the water surface.* Thalli reproducing
vegetatively by budding from one or two pouches on the sides, the parent thallus
and budded thalli often cohering in groups of 2-several, each thalloid segment
commonly referred to as a "frond." Roots, if present, 1-several
hanging down from near the center on the underside of each frond, short, unbranched,
fine. Flowers rarely present, imperfect, contained in tiny reproductive
pouches or pits at the edge (Lemna, Spirodela) or on the upper
surface (Wolffia) of the frond, subtended by a spathe within the reproductive
pouch; perianth none, staminate flowers 1 or 2, each comprised of a single
anther on a short filament; pistillate flower 1, contained in the same
pouch as the staminate flower(s), consisting of a single flask-shaped ovary.
Fruit autricle containing 1-few seeds.
*The aquatic liverworts, Riccia and Ricciocarpus are occasionally
encountered in fresh waters of this region. These nonvascular plants resemble
the duckweeds in size and growth habit and, in fact, are sometimes collected
with duckweeds. Riccia fluitans appears as a very narrow (ca. 1 mm
wide), bifurcating, ribbonlike thallus, free-floating and lacking rhizoids.
Ricciocarpus natans has a broadly lobed rosette form with numerous
rhizoids on the underside. When stranded on mud, the thallus is nearly radially
symmetric with the rhizoids anchored in the substrate. The free-floating form
is more bilaterally symmetric with conspicuous reddish rhizoids trailing beneath
Clark, H. L. and J. W. Thieret. 1968. The duckweeds of Minnesota.
Michigan Bot. 7:67-75
Daubs, E. H. 1965. A monograph of Lemnaceae. Illinois Biol. Monogr.
Hartog, C. den and F. van der Plas. 1970. A synopsis of the Lemnaceae.
Landolt, E. 1980. Biosystematic investigation of the family of duckweeds
(Lemnaceae), vol. 1. Veroff. Geobot. Inst. ETH, Stiftung Rubel,
||Fronds thickened, less than 1.5 mm long, lacking
||Fronds flat, mostly longer than 1.5 mm long, with
1-several roots trailing from the lower side.
||Each frond with 3 or more roots; underside of the
frond solid purple.
||Each frond with a single root; underside of the
frond green or purple-tinged or mottled.
60. Lemnaceae, the Duckweed Family
1. Lemna L. -- Duckweed
2. Spirodela Schleid. -- Duck-meat
- 1. Lemna aequinoctialis Welw.
- 2. Lemna gibba L.
- 3. Lemna minor L.
- 4. Lemna minuscula Herter
- 5. Lemna obscura (Austin) Daubs
- 6. Lemna perpusilla Torr.
- 7. Lemna trisulca L. -- Star duckweed
- 8. Lemna turionifera Landolt
3. Wolffia Horkel -- Water-meal
- 1. Spirodela polyrrhiza (L.) Schleid.
- 1. Wolffia borealis (Engelm.) Landolt
- 2. Wolffia columbiana Karst.
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