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Isoetes engelmannii — Engelmann's quillwort

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Facts

Engelmann's quillwort inhabits shallow waters of lakes and rivers in New England south of Maine. The species is endemic to eastern North America, and can be locally abundant.

Habitat

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

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
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf shape
the vegetative leaves are long and narrow
Spore leaf arrangement
the sporophylls are located in a whorl at the base of the plant
Form of shoot
NA
Horizontal stem
NA
Leaf differences
the vegetative leaves within a node are all similar in size and shape
Teeth on leaf edges
the edges of the vegetative leaves have no teeth
Constriction zones
  • NA
  • NA
Spore leaf length
600–900 mm
Leaf outline
the vegetative leaves are long and very narrow (linear)
Show all characteristics

  • Clonal plantlets

    Gemma arrangement
    NA
    Gemma shape
    NA
    Gemma width
    0 mm

  • Leaves

    Leaf differences
    the vegetative leaves within a node are all similar in size and shape
    Leaf length
    600–900 mm
    Leaf orientation
    • the vegetative leaves spread away from the stem
    • the vegetative leaves spread slightly away from the stem, at a steep angle
    Leaf outline
    the vegetative leaves are long and very narrow (linear)
    Leaf ranks
    NA
    Leaf shape
    the vegetative leaves are long and narrow
    Spore leaf length
    600–900 mm
    Teeth on leaf edges
    the edges of the vegetative leaves have no teeth

  • Place

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

  • Spores or spore cones

    Cone base at stem
    NA
    Cone stalk branching
    NA
    Cone thickness
    0 mm
    Cone width
    0 mm
    Length of cone
    0 mm
    Number of cones
    0
    Quillwort itssue covering spores
    the velum covers less than half of the spores
    Same or different spores
    there are two different types of spores present
    Spore diameter
    0.4–0.56
    Spore girdle
    there is no girdle alongside the equatorial ridge
    Spore leaf arrangement
    the sporophylls are located in a whorl at the base of the plant
    Spore leaf lifespan
    the sporophylls remain green for the life of the plant
    Spore leaf orientation
    the sporophylls slant upwards at a steep angle
    Spore leaf shape
    the spore-bearing leaves are long and narrow
    Spore leaf teeth
    The edges of the spore-bearing leaves are smooth, and without teeth
    Spore texture
    the spore surface has a net-like pattern on it (reticulate)
    Sporophyll ranks
    NA
    Sterile tip of cone
    NA

  • Stem, shoot, branch

    Branch cross-section
    NA
    Branch form
    NA
    Constriction zones
    • NA
    • NA
    Form of shoot
    NA
    Horizontal stem
    NA
    Horizontal stem length
    0 mm
    Horizontal stem thickness
    0 mm
    Stem height
    0 mm

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.

Massachusetts
fairly widespread (S-rank: S4)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Rhode Island
extremely rare (S-rank: S1), concern (uncertain) (code: C*)
Vermont
extremely rare (S-rank: S1), threatened (code: T)

var. engelmannii

Massachusetts
unranked (S-rank: SNR)

From Flora Novae Angliae dichotomous key

3.  Isoetes engelmannii A. Braun N

Engelmann’s quillwort. CT, MA, ME, NH, RI, VT. Shallow water of lakes and rivers, 
sometimes emergent.

2×3. Isoetes echinospora × Isoetes engelmannii → Isoetes ×‌eatonii Dodge is a relatively rare quillwort hybrid known from CT, MA, NH, RI. It shows megaspore ornamentation similar to I. riparia (i.e., a pattern intermediate between spines and ridges, usually appearing as columns that sometimes merge to form broken ridges). However, I. ×‌eatonii will have polymorphic megaspores rather than the uniform megaspore morphology of I. riparia.

3×7. Isoetes engelmannii × Isoetes riparia → Isoetes ×‌brittonii D.F. Brunton & W.C. Taylor is documented from only 
CT in New England. It has megaspores with ornamentation very similar to those of 
 I. engelmannii, except that the ridges forming the reticulum are broken in places 
and get more congested toward the equatorial ridge (similar to I. riparia). The well-formed megaspores measure 0.47–0.56 mm in diameter.

3×8. Isoetes engelmannii × Isoetes tuckermanii → Isoetes ×‌foveolata A.A. Eat. ex Dodge is a rare quillwort hybrid known from CT, NH; also reported from MA by Magee and Ahles (1999), but specimens are unknown. The megaspores show a broken reticulum that is shorter and denser near the equatorial ridge (i.e., the megaspores have a somewhat apparent girdle). The megaspores measure 0.38–0.56 mm in diameter.

Native to North America?

Yes

Sometimes confused with

Isoetes riparia:
megaspores 0.45–0.65 mm in diameter, averaging more than 0.5 mm, reticulate with broken or anastomosing ridges (vs. I. engelmannii, with megaspores 0.4–0.56 mm in diameter, averaging less than 0.5 mm, patterned with an unbroken reticulum).

Family

Isoetaceae

Genus

Isoetes