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Cystopteris tenuis — Mackay's fragile fern

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Facts

Mackay's fragile fern is a hybrid whose parents were, most likely, Southern fragile fern (Cystopteris protrusa) and an extinct relative of fragile fern.

Habitat

Cliffs, balds, or ledges, ridges or ledges, talus and rocky slopes

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf divisions
  • the leaf blade is compound (divided into leaflets)
  • the leaf blade is twice compound (divided into leaflets, which are further divided into leaflets)
Plant growth form
the leaves grow from a rhizome growing at or below the ground
Spore-bearing leaflets
the spore-bearing fronds are similar in size and shape to the sterile fronds
Sorus shape
the sori are circular or kidney-shaped
Leaf stalk scales
the leaf stalk has scales
Leaf stalk hairs
there are no hairs on the leaf stalk
Leaf blade length
5–30 cm
Leaf vein tips
the veins go all the way to the edge of the leaf blade
Show all characteristics

  • Growth form

    Life form
    the plant is herbaceous and terrestrial
    Life stage
    the plant is visible as a typical leaf-bearing fern (sporophyte)
    Spore-bearing leaflets
    the spore-bearing fronds are similar in size and shape to the sterile fronds

  • Leaves

    Features of leaves
    there are no special features on the leaves
    Leaf blade length
    5–30 cm
    Leaf blade shape
    • the leaf blades are widest above the base, then taper narrowly towards the tip (lanceolate)
    • the leaf blades are widest near the middle and tapered towards the base and tip (elliptic)
    Leaf blade width
    At least 3 cm
    Leaf divisions
    • the leaf blade is compound (divided into leaflets)
    • the leaf blade is twice compound (divided into leaflets, which are further divided into leaflets)
    Leaf lifespan
    the leaves drop off in winter
    Leaf stalk color
    yellow to brown
    Leaf stalk hairs
    there are no hairs on the leaf stalk
    Leaf stalk length
    30–272 mm
    Leaf stalk relative length
    the leaf stalk is more than three quarters as long as the blade
    Leaf stalk scale location
    the scales are present only on the lower half of the leaf stalk
    Leaf stalk scales
    the leaf stalk has scales
    Leaf stalk vessels
    2 bundles
    Leaf vein branching
    the secondary veins of the leaf blade branch dichotomously (two equal branches at each branch point)
    Leaf vein tips
    the veins go all the way to the edge of the leaf blade
    Leaflet relative size
    the bottom leaflets are about half as long as, to slightly longer than, the leaflets from the middle of the frond
    Leaflet stalks
    the leaflets are stalked
    Lobe or leaflet length
    8–70 mm
    Lobe or leaflet pairs
    9–15
    Lobe or leaflet shape
    • the lobe or leaflet is shaped like an ellipse; widest near the middle and tapering at both ends
    • the lobe or leaflet is widest below the middle and broadly tapering at both ends; egg-shaped
    Lobe or leaflet width
    5–33 mm
    Plant growth form
    the leaves grow from a rhizome growing at or below the ground
    final leaf segment margin
    the topmost lobe or leaflet of the leaf blade has an edge with teeth

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • cliffs, balds, or ledges
    • ridges or ledges
    • talus or rocky slopes

  • Spores or spore cones

    Sorus features
    there are no special features on the sorus
    Sorus shape
    the sori are circular or kidney-shaped
    Sporangia location
    the spores are clustered on sori on the lower surface of the leaf blade
    Sporangium type
    the sporangia are opaque without an annulus and usually without a stalk (leptosporangiate)
    Spore forms
    there is only one type of spore present

Wetland status

Not classified

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
widespread (S-rank: S5)

From Flora Novae Angliae dichotomous key

5.  Cystopteris tenuis (Michx.) Desv. N

Mackay’s fragile fern. Cystopteris fragilis (L.) Bernh. var. mackayi Lawson • CT, MA, ME, NH, RI, VT. On boulders and thin soil over rock, occasionally on cliff faces.

2×5. Cystopteris fragilis × Cystopteris tenuis → Recognition of this nothospecies is generally missed during floristic inventories; it is most commonly misidentified as Cystopteris tenuis. It is intermediate between the two parental taxa, though on average larger than either, and possesses abortive spores.

Native to North America?

Yes

Sometimes confused with

Cystopteris fragilis:
leafules on basal leaflets unstalked, +/- truncate, and emerging perpendicular to leaflet axis (vs. C. tenuis, with leafules on basal leaflets short-stalked, tapering to base, and angled to lean toward tip of leaflet).
Cystopteris protrusa:
leaves clustered 1–4 cm behind the apex of the rhizome, rhizome pubescent, especially toward apex, with yellow hairs, and leafules, especially those of the basal medial portion of the blade, borne on evident stalks (vs. C. tenuis, with leaves clustered near rhizome apex, rhizome lacking hairs, and leafules varying from sessile to short-stalked).

Synonyms

  • Cystopteris fragilis var. mackayi Lawson

Family

Woodsiaceae

Genus

Cystopteris