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Cystopteris

Cystopteris is a difficult genus due to hybridization (past and present) and the occasional presence of fertile, but stunted, plants in stressful habitats. Hybrids are best determined  by examination of spores, which are usually abortive. In order to correctly determine stunted plants, specimens should include rhizomes and complete petioles, as well as carefully preserved leaf blades. Further, for species superficially similar to C. fragilis, it is best to  have several collections to adequately capture variation within the population. Reference: Haufler et al. (1993a).

See list of 2 species in 1a
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1a. Rachises, costae, and indusia sparsely to densely stipitate-glandular; bulbils often present on the abaxial blade surface (these rare and misshapen in C. laurentiana); leaf blades widest at or near base
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  C. bulbifera
  2a. Leaf blade triangular to long-triangular; bulbils frequently present; leaf rachis,  costae, costules, and ultimate segments usually with dense glandular hairs; spores mostly 33–38 μm in diameter
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  C. laurentiana
  2b. Leaf blade ovate to narrow-ovate; bulbils only rarely present, misshapen; leaf rachis, costae, costules, and ultimate segments with sparse glandular hairs (these often absent from herbarium specimens); spores mostly 49–60 μm in diameter
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1b. Rachises, costae, and indusia without glandular hairs; plants lacking bulbils; blade lanceolate to elliptic
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  C. protrusa
  3a. Leaves clustered 1–4 cm behind the apex of the rhizome; rhizome pubescent, especially toward apex, with yellow hairs; leafules, especially those of the basal medial portion of the blade, borne on evident stalks; petiole green to stramineous, with dark pigmentation only at the very base; spores mostly 28–34 μm in diameter
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  3b. Leaves clustered near rhizome apex; rhizome lacking hairs; leafules varying from sessile to short-stalked; petiole with dark brown color not confined to the base, the pigmentation extending apically for a noticeable distance;
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    C. fragilis
    4a. Basal leafules sessile or nearly so, broadly tapering or rounded at the base, approximate, emerging nearly perpendicular to the costa [Fig. 35]; apical portion of blade with deltate to ovate leaflets; margins of leafules serrate; acroscopic margin  of leaflet convex due to the fact that the costa of the leaflet is nearly straight; indusia  up to 1 mm long
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    C. tenuis
    4b. Basal leafules short-stalked, mostly cuneate at the base, remote, emerging at  an acute angle to the costa (i.e., ascending) [Fig. 37]; apical portion of blade with ovate to narrowly elliptic leaflets; margins of leafules crenate; acroscopic margin of leaflet concave due to the fact that the costa of the leaflet curves slightly upward; indusia up to 0.5 mm long

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Show photos of: Each photo represents one species in this genus.