Isoetes riparia Engelm. ex A. Braun

Canada shore quillwort

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

Canada shore quillwort inhabits sandy and muddy margins of streams and lakes, including tidal shorelines. It is rare in our region, but is at least historically known from every New England state.

Habitat

Brackish or salt marshes and flats, fresh tidal marshes or flats, shores of rivers or lakes

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
Spore leaf length
350–500 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
    350–500 mm
    Leaf orientation
    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
    350–500 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
    • brackish or salt marshes and flats
    • fresh tidal marshes or flats
    • 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
    0.4499–0.6499
    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 is crested with a narrow irregular ridge (cristate)
    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)

New England Distribution and Conservation Status

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.

Connecticut
uncommon to fairly widespread (S-rank: S3S4)
Massachusetts
unranked (S-rank: SNR)
Vermont
rare (S-rank: S2)

var. amesii

Massachusetts
unranked (S-rank: SNR)

var. canadensis

Maine
historical (S-rank: SH), potentially extirpated (code: PE)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Rhode Island
extremely rare (S-rank: S1), concern (code: C)

var. riparia

Massachusetts
unranked (S-rank: SNR)

Native to North America?

Yes

Sometimes Confused With

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

Synonyms

  • Isoetes canadensis (Engelm.) A.A. Eat. ex Maxon, nom. illeg.

Family

Isoetaceae

Genus

Isoetes

Notes on Subspecies and Varieties in New England

Our variety is Isoetes riparia Engelm. ex A. Braun var. canadensis Engelm. ex N.E. Pfeiff.

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Information from Dichotomous Key of Flora Novae Angliae

7.  Isoetes riparia Engelm. ex A. Braun var. canadensis Engelm. ex N.E. Pfeiff. N

Canada shore quillwort. Isoetes canadensis (Engelm.) A.A. Eat. ex Maxon, nom. illeg.CT, MA, ME, NH, RI, VT. Sandy and muddy margins of streams and lakes, including tidal shorelines. Isoetes riparia var. canadensis is an allotetraploid, formed by chromosome doubling in 
 I. ×‌eatonii, which is the first generation hybrid between I. echinospora and I. engelmannii. See Caplen and Werth (2000) for justification of recognizing northern populations of the I. riparia complex as distinct. Unfortunately, no combination at the specific level has yet been made.

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.

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.

7×8. Isoetes riparia × Isoetes tuckermanii Isoetes ×‌novae-angliae D.F. Brunton & D.M. Britt. is a rare quillwort hybrid known from CT, MA, NH. It has polymorphic megaspores, the well-formed ones measuring mostly 0.45–0.53 mm in diameter and having a dense, broken reticulum, showing an obscure girdle of congested reticulum (no spine-like papillae as occur in I. tuckermanii).