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Wolffia borealis — northern water-meal

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Facts

Northern water-meal is absent from much of northern New England, except in Vermont's Champlain Valley. Water-meal (Wolffia) species have no roots. In a study comparing northern water-meal with common duckweed (Lemna minor) and common duck-meal (Spirodela polyrrhiza), northern water-meal had the fastest rate of production (0.62 fronds per day).

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
aquatic
New England state
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Roots
there are no roots on the plant
Thallus shape in cross-section
the thallus is somewhat flattened on at least one side in cross-section
Thallus length
0.7–1.5 mm
Thallus shape
the thallus is another shape in outline
Thallus dimensions
1.3–2
Veins on upper surface
0
Show all characteristics

  • Flowers

    Scale surrounding flower
    no
    Stamen number
    1

  • Fruits or seeds

    Seed surface ribbed
    the seed surface is nearly smooth

  • Growth form

    Root length
    0 mm
    Root number
    0
    Root sheath winged at base
    NA
    Roots
    there are no roots on the plant
    Roots perforating basal scale
    NA
    Thallus dimensions
    1.3–2
    Thallus edge
    the edge of the thallus is smooth (without teeth) near the tip
    Thallus length
    0.7–1.5 mm
    Thallus shape
    the thallus is another shape in outline
    Thallus shape in cross-section
    the thallus is somewhat flattened on at least one side in cross-section
    Thallus stalks
    the thallus does not have a stalk
    Thallus width
    0.4–1.2 mm
    Thallus with red pigment
    no
    Turions
    yes

  • Leaves

    Papilla on thallus
    no
    Veins on upper surface
    0

  • Place

    Habitat
    aquatic
    New England state
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

In New England

Distribution

Connecticut
absent
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
absent
Vermont
present

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
unranked (S-rank: SNR)

From Flora Novae Angliae dichotomous key

1.  Wolffia borealis (Engelm. ex Hegelm.) Landolt ex Landolt & Wildi N

northern water-meal. Wolffia brasiliensis Weddell var. borealis Engelm. ex Hegelm.; W. punctata, auct. non Griseb. • MA, ME, NH, VT; also reported from CT by Landolt (2000), but specimens are unknown; extending north in the Lake Champlain Valley but absent over much of northern New England. Mesotrophic to eutrophic waters of lakes, rivers, and backwaters.

Native to North America?

Yes

Sometimes confused with

Wolffia columbiana:
plants spherical to ovoid, not flattened on the upper surface, without any upward bent points (vs. W. borealis, with plants flattened on top and with an upward bent point at each end).
Wolffia brasiliensis:
thalli rounded at each apex, with a large, prominent papilla in the center of the upper surface, 1–1.5 times as long as wide (vs. W. borealis, with thalli with a minute, upward-bent point at each apex, lacking a central papilla, 1.3–2 times as long as wide).

Synonyms

  • Wolffia brasiliensis Weddell var. borealis Engelm. ex Hegelm.
  • Wolffia punctata, misapplied

Family

Araceae

Genus

Wolffia