Wolffia columbiana Karst.
Columbian water-meal (Columbian watermeal)
Lemnaceae
Introduction to Vascular Plants
Columbian water-meal (Columbian watermeal)
Lemnaceae
Introduction to Vascular Plants
Introduction
This is a tiny floating perennial aquatic plant that lacks roots and definite leaves or stems. It is clonal and occurs in thick populations that often appear as scum on the surface of still waters, such as ditches, ponds, and lake edges. It is distinctly smaller than the more familiar duckweed (Lemna minor). View a comparative photo. In North America, Columbian water-meal is found across the US (though absent from AZ, NM, UT, CO, ID, WY, WA) and Canada (AB, BC, MB, NB, ON, QC, SK) (USDA 2010). In BC, it is so far reported only from southwestern Vancouver Island, from Swan Lake. However, it might be overlooked and should be looked for, for example, in the Lower Mainland.
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Species Information
General:
Fronds annual, free-floating, globe-shaped, about as long as wide, 0.8-1.3 mm long, transparent green, round except for flat center with 1 to 10 (30) stomates, usually in unequal pairs, rootless, with a pouch at the basal end from which young plants arise.
Flowers:
Two, together on the upper surface, 1 female, 1 male; stamen 1; pistil 1.
Fruits:
Utricles (inflated fruits), globe-shaped; seeds 1, smooth. vol6_8
Illustration
If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.
Illustration Source: The Illustrated Flora of British Columbia
Habitat and Range
Ponds and lakes in the lowland zone; rare in SW BC, known only from the Saanich Peninsula; E to PQ and S to MA, PA, FL, MS, TX, CO and CA; S. America.Status Information
Synonyms
Synonyms and Alternate Names:
Bruniera columbiana (Karst.) Nieuwl.
Similar Species
In Washington, Columbian water-meal is found in association with northern water meal (Wolfia borealis), which is found in BC, and Brazilean water-meal (Wolffia brasiliensis), which is not reported from BC. Colour, shape and number of pores are used to separate it from these species (Washington Department of Natural Resources 2005). In the field, W. borealis and W. brasiliensis are dark green in colour, and W. columbiana is a translucent green (Hickman 1993). In Washington, Wolffia columbiana is found at elevations of 10 to 250 ft. (Washington Department of Natural Resources 2005). The elevational range in BC is presently unknown.
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Taxonomic Keys
1. Frond elliptical to egg-shaped, nearly twice as long as wide, with point at apex bent upwards.......W. borealis
1. Frond globe-shaped, about as long as wide............................W. columbiana |
References
Hickman, James C. 1993. The Jepson Manual of the Higher Plants of California. University of California Press, Los Angeles.
Washington Department of Natural Resources. 2005. Wolffia columbiana page. On-line Field Guide to Selected Rare Plants of Washington. Washington Department of Natural Resources, Washington Natural Heritage Program and the U.S.D.I. Bureau of Land Management.