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Potamogeton bicupulatus — snail-seed pondweed

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Facts

The unusual name of this plant, snail-seed pondweed, refers to the fact that the embryo inside the seed has a distinctive morphology, coiled in a full spiral. In New England, it is mainly found in lakes and rivers on the coastal plain except for a disjunct population in Vermont.

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
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf position
  • some of the leaves are floating at the surface of the water
  • the leaves are all submerged underwater
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade length
15–110 mm
Petal or sepal number
there are four petals, sepals, or tepals in the flower
Petal color
  • brown
  • green
Specific leaf type
the leaf is not divided, rather the blade is made up of one segment
Floating leaf shape
  • the leaf blade is elliptic (widest near the middle and tapering at both ends)
  • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
Underwater leaf blade width
0.1–0.4 mm
Fruit type (general)
  • the fruit is dry but does not split open when ripe
  • the fruit is fleshy
Underwater leaf length
15–110 mm
Show all characteristics

  • Clonal plantlets

    Turion length
    0 mm

  • Flowers

    Carpels fused
    the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Flower lower lip length
    0 mm
    Flower position
    • the flowers are above the surface of the water
    • the flowers are below the surface of the water
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Inflorescence length
    1.5–14 mm
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Length of peduncle
    1–22 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    4
    Ovary position
    the sepals and/or petals are attached below the ovary
    Palate on corolla
    no
    Petal and sepal arrangement
    the flower includes only one cycle of petals or sepals
    Petal appearance
    the petals are green and/or leafy in texture
    Petal color
    • brown
    • green
    Petal fringed edges
    the petals are not fringed
    Petal hairs on inner/upper surface
    there are no hairs on the inner/upper petal surface
    Petal number
    4
    Petal or sepal number
    there are four petals, sepals, or tepals in the flower
    Pistil number
    4
    Sepal appearance
    NA
    Sepal length
    0 mm
    Sepal number
    0
    Sepals fused only to sepals
    NA
    Spur length
    0 mm
    Stamen number
    4
    Stamen position relative to petals
    NA
    Stamens fused to petals
    the stamens are fused near the bases of the petals or tepals
    Style number
    4

  • Fruits or seeds

    Fruit beak length
    0 mm
    Fruit length
    1.1–2.1 mm
    Fruit type (general)
    • the fruit is dry but does not split open when ripe
    • the fruit is fleshy
    Fruit type (specific)
    • the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)
    • the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
    Fruit width
    1.1–2 mm

  • Glands or sap

    Oil glands on nodes
    none of the nodes have oil glands
    Sap
    the sap is clear and watery

  • Growth form

    Lifespan
    the plant lives more than two years
    Root septa
    the roots do not have transverse septa
    Roots floating in water
    there are no clusters of roots floating in the water
    Turions
    there are no turions on the plant
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Bract position (Sparganium)
    NA
    Bract relative length
    At least 3854 mm
    Bracts
    neither the flowers nor their pedicels have bracts
    Floating leaf basal lobes
    no
    Floating leaf blade width
    1–11 mm
    Floating leaf length
    6–28 mm
    Floating leaf shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    Floating leaf tip
    the tip of the floating leaf blade is acute (sharply pointed)
    Floral bract form
    NA
    Floral bract length
    0 mm
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade length
    15–110 mm
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    0.1–0.6 mm
    Leaf position
    • some of the leaves are floating at the surface of the water
    • the leaves are all submerged underwater
    Leaf special features
    none of the mentioned special features are present
    Leaf-like branch segments
    0
    Leaf-like branch shape
    NA
    Specific leaf type
    the leaf is not divided, rather the blade is made up of one segment
    Staminate bract edge (Myriophyllum)
    NA
    Stipule appearance
    the stipules are firm or fibrous, and colored white, green or brown
    Stipule fused to leaf
    the stipules are not attached to the leaf blade at all
    Stipules
    the plant has stipules
    Stipules fused around stem
    the stipules do not forma closed tube around the stem
    Trap-bladder length
    0 mm
    Underwater leaf air passage number
    At least 1439
    Underwater leaf air passage relative width
    At least 4336
    Underwater leaf air passage row number
    0
    Underwater leaf blade edges
    the underwater leaf has smooth edges, without teeth
    Underwater leaf blade shape
    the underwater leaf blade is linear (very narrow with more or less parallel sides)
    Underwater leaf blade veins
    1
    Underwater leaf blade width
    0.1–0.4 mm
    Underwater leaf length
    15–110 mm
    Underwater leaf stalk
    no
    Underwater leaf stalk length
    0 mm
    Underwater leaf tip shape
    the tip of the underwater leaf is acute (sharply pointed)
    Veins in floating leaf
    3–7

  • Place

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

  • Stem, shoot, branch

    Flowering stem growth form
    • the flowering stem is upright
    • the flowering stem trails along the substrate, or floats in the water

Wetland status

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

In New England

Distribution

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

Conservation status

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

Maine
uncommon (S-rank: S3), special concern (code: SC)
Massachusetts
widespread (S-rank: S5)
Vermont
rare (S-rank: S2)

From Flora Novae Angliae dichotomous key

4.  Potamogeton bicupulatus Fern. N

snail-seed pondweed. Potamogeton capillaceus Poir., pro parte; P. diversifolius Raf. var. trichophyllus Morong • CT, MA, ME, NH, RI, VT; mainly on the coastal plain but disjunct to Essex County, VT. Shallow, still or slow-moving, acidic to circumneutral water of lakes and rivers.

4×7. Potamogeton bicupulatus × Potamogeton epihydrus → Potamogeton ×‌aemulans Z. Kaplan, Hellquist, & Fehrer is a rare pondweed hybrid responsible for reports of Potamogeton diversifolius Raf. in New England. It has submersed leaves 0.2–1.8 mm wide that are 3 (–5)-veined, with or without a narrow 
band of lacunae bordering the midrib. The stipules are 3–34 mm long, mostly distinct from the leaf but some connate for a short distance (up to 2.8 mm). The floating leaves, which are always present on flowering plants, are 18–35 ×5–11 mm and have 9–15 
veins. The hybrid shows dimorphic inflorescences (within a population), with some short ones (2–3 mm) in the axils of submerged leaves and longer ones (3–6 mm) in emersed spikes. This hybrid is known from CT, MA, and is found primarily in slow-moving, circumneutral water of rivers.

Native to North America?

Yes

Sometimes confused with

Potamogeton spirillus:
submersed leaf blades 0.5–2 mm wide, the apex obtuse to acute, fused portion of the stipule usually equal to or longer than the distinct portion, and apex of floating leaves obtuse (vs. P. bicupulatus, with submersed leaf blades 0.1–0.4 mm wide, the apex acute to long-tapering, fused portion of the stipule usually shorter than the distinct portion, and apex of floating leaves acute).

Synonyms

  • Potamogeton capillaceus Poir., pro parte
  • Potamogeton diversifolius Raf. var. trichophyllus Morong

Family

Potamogetonaceae

Genus

Potamogeton