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Lemna perpusilla — minute duckweed

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Facts

Minute duckweed is a native plant that, in New England, occurs in quiet, nutirent-rich waters of Maine, Connecticut, Massachusetts, and Vermont. Its species name, "perpusilla" derives from the Latin words for "extra" and "very small." Its "leaves" (thalli) often have a tiny projection (papilla) at the tip, and its roots are quite short, only up to 3.5 cm (a little longer than 1 inch) long.

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
  • Massachusetts
  • Rhode Island
  • Vermont
Roots
there is approximately one root per thallus
Thallus shape in cross-section
the thallus is somewhat flattened on at least one side in cross-section
Thallus length
1–4 mm
Thallus shape
  • the thallus is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
  • the thallus is ovate (egg-shaped)
Thallus dimensions
1–1.7
Veins on upper surface
3
Show all characteristics

  • Flowers

    Scale surrounding flower
    no
    Stamen number
    2

  • Fruits or seeds

    Fruit length
    0.7–1 mm
    Seed surface ribbed
    the seed surface is nearly smooth

  • Growth form

    Root length
    Up to 35 mm
    Root number
    1
    Root sheath winged at base
    yes
    Roots
    there is approximately one root per thallus
    Roots perforating basal scale
    there is no basal scale on the plant
    Thallus dimensions
    1–1.7
    Thallus edge
    the edge of the thallus is smooth (without teeth) near the tip
    Thallus length
    1–4 mm
    Thallus shape
    • the thallus is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    • the thallus is ovate (egg-shaped)
    Thallus shape in cross-section
    the thallus is somewhat flattened on at least one side in cross-section
    Thallus stalks
    the thallus has a stalk
    Thallus with red pigment
    no
    Turions
    no

  • Leaves

    Papilla on thallus
    yes
    Veins on upper surface
    3

  • Place

    Habitat
    aquatic
    New England state
    • Massachusetts
    • Rhode Island
    • 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
absent
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
Vermont
present

Conservation status

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

Massachusetts
historical (S-rank: SH), H (code: H)
Rhode Island
extremely rare (S-rank: S1), concern (uncertain) (code: C*)
Vermont
historical (S-rank: SH)

From Flora Novae Angliae dichotomous key

3.  Lemna perpusilla Torr. NC

minute duckweed. Lemna perpusilla Torr. var. trinervis Austin • MA, RI, VT; also reported 
from CT by Hellquist and Crow (1982), but specimens are unknown. Mesotrophic to 
eutrophic waters of lakes, rivers, beaver flowages, and pools. The report of Lemna perpusilla from ME by Landolt (2000) was in error. The voucher specimen was L. minor (Elias Landolt, personal communication).

Native to North America?

Yes

Sometimes confused with

Lemna turionifera:
root sheath not winged at base, roots to 15 cm long, frequently longer than 3.5 cm, rounded at apex, and thalli usually with anthocyanic pigment (vs. L. purpusilla, with the root sheath winged at base, roots up to 3.5 cm long, usually sharply pointed at apex, and thalli without anthocyanic pigment).
Lemna minor:
root sheath not winged at base, roots to 15 cm long, frequently longer than 3.5 cm, rounded at apex, and thalli often with at least some spotting or diffuse coloring with anthocyanic pigment (vs. L. purpusilla, with the root sheath winged at base, roots up to 3.5 cm long, usually sharply pointed at apex, and thalli without anthocyanic pigment).

Synonyms

  • Lemna perpusilla Torr. var. trinervis Austin

Family

Araceae

Genus

Lemna