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C. laurentiana resources
and comparison with C. bulbifera, C. fragilisand comparison with C. bulbifera, C. fragilis
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Cystopteris laurentiana (Weatherby) Blasdell

Laurentian bladder fern

Etymology Laurentiana describes the area around the St. Lawrence River.
Description Rhizome: short-creeping, covered with old stipe bases, scales tan to light brown, lanceolate, somewhat clathrate.
Frond: 50 cm high by 12 cm wide, deciduous, monomorphic, nearly all fronds fertile, blade/stipe ratio: 3:2.
Stipe: stipes --3 to 8-- clustered at stem apex, grooved, brown at base to straw-colored above, sparsely scaly at base, vascular bundles: 2, round or oblong.
Blade: 2-pinnate-pinnatifid, ovate to lanceolate, usually widest above base, rarely bearing bulblets on the rachis, herbaceous, light green or yellowish-green, sparsely present gland-tipped hairs on rachis and costa.
Pinnae: 12 to 16 pair, perpendicular to the rachis, opposite, lanceolate; costae grooves above continuous from rachis to costae; margins serrate; veins free, simple or forked, directed into teeth and notches.
Sori: round, in 1 row between midrib and margin, indusium: cup-shaped, beneath sorus on midrib side, on a vein, sporangia: brown to black, maturity: midsummer to early fall.
Culture Habitat: cracks and ledges on cliffs, often on calcareous substrates . Distribution: north central North America to northeastern North America, but not boreal, uncommon or pehaps misidentified as C. fragilis. Hardy to -40C, USDA Zone 2.
Distinctive Characteristics Smaller than C. bulbifera, with brown, not maroon or reddish stipes, blade widest above the base, veins sometimes running to the teeth tips, rarely with bulbils. Larger than C. fragilis, with more pinnae, veins sometimes running to the notches.
Cystopteris fragilis (Linnaeus) Bernhardi var. laurentiana Weatherby
Cystopteris laurentiana
Cystopteris laurentiana. frond, intermediate between parents C. bulbifera and C. fragilis.  Illustration by V. Fulford from Ferns and Fern Allies of Canada, William J. Cody and Donald M. Britton, 1989, Agriculture Canada, used with permission.
Parents C. bulbifera and C. fragilis, and it is intermediate in several respects. The frond of the former is generally over 50 cm, the latter under 30 cm, while this is in the range 30-50 cm. The veins run to the notches in C. bulbifera, to the teeth in C. fragilis, to both here. This has 12-16 pinnae pairs, C. bulbifera has more, and C. fragilis less.
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