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Isoetes echinospora — spiny-spored quillwort

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Facts

The leaves of spiny-spored quillwort can vary in size, color, and form. It is the most common quillwort found in lakes and ponds of New England that are low in nutrients and somewhat acidic. It may form hybrids with several other quillworts (Isoetes).

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 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
Spore leaf length
0–400 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
    Up to 400 mm
    Leaf orientation
    • the vegetative leaves curve outwards and downwards from the main stem
    • 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
    0–400 mm
    Teeth on leaf edges
    the edges of the vegetative leaves have no teeth

  • Place

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

  • 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
    0.399–0.549
    Spore girdle
    NA
    Spore leaf arrangement
    the sporophylls are located in a whorl at the base of the plant
    Spore leaf lifespan
    the sporophylls wither and fall off at the end of the growing season
    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 spines on it (echinate)
    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.

ssp. muricata

Massachusetts
widespread (S-rank: S5)
Rhode Island
extremely rare (S-rank: S1), concern (uncertain) (code: C*)

Subspecies and varieties

Our subspecies is Isoetes echinospora Durieu ssp. muricata (Durieu) A. & D. Löve.

From Flora Novae Angliae dichotomous key

2.  Isoetes echinospora Durieu ssp. muricata (Durieu) A. & D. Löve N

spiny-spored quillwort. Isoetes braunii Durieu; I. echinospora Durieu var. braunii (Durieu) Engelm.; I. muricata Durieu • CT, MA, ME, NH, RI, VT; throughout New England and one 
of the more common quillworts. Shallow, slightly acidic lakes and slow-moving streams. 
North American plants of Isoetes echinospora differ morphologically from Old World 
plants in that the leaves bear stomata (those from the Old World do not). This fact, 
combined with geographic separation, warrants recognition of North American plants 
as a distinct subspecies.

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.

2×7. Isoetes echinospora × Isoetes riparia → Isoetes ×‌dodgei A.A. Eat. is a rare quillwort hybrid known from NH, VT. It 
shows spiny megaspores, but many of the spines are fused and/or irregular, resulting 
in a convoluted-echinate surface (i.e., the spines are not as regular in appearance 
as those in I. echinospora). The well-formed megaspores are usually smaller than 0.54 mm in diameter.

2×8. Isoetes echinospora × Isoetes tuckermanii → Isoetes ×‌echtuckerii D.F. Brunton & D.M. Britt. is known from MA, ME, NH, but should be expected anywhere the two parental species are found together. It has megaspores that show isolated columns and short, broken ridges that become shorter and more congested near the equatorial ridge (i.e., the hybrid megaspores have a somewhat apparent girdle, which is present in I. tuckermanii but lacking in I. echinospora). The well-formed megaspores are mostly 0.46–0.50 mm in diameter.

Native to North America?

Yes

Synonyms

  • Isoetes braunii Durieu
  • Isoetes echinospora var. braunii (Durieu) Engelm.
  • Isoetes muricata Durieu

Family

Isoetaceae

Genus

Isoetes