Cystopteris montana (Lamarck) Bernhardi ex Desvaux

Mountain bladder fern

Etymology Montana is the word for the mountains.
Description Rhizome: long-creeping, cordlike, internodes 1--2 cm, whitish at tip, scales usually tan to light brown, ovate-lanceolate.
Frond: 40 cm high by 15 cm wide, deciduous, monomorphic, blade/stipe ratio: 1:3 to 1:1.
Stipe: dark brown to black at base, gradually becoming green or straw-colored above, sparsely scaly throughout, vascular bundles: 2, round or oblong.
Blade: 3-pinnate-pinnatifid or more, equilaterally triangular, similar to a Gymnocarpium in form, firm, translucent, pale green, rachis and costae with tan, multicellular gland-tipped hairs.
Pinnae: 7 to 8 pair, anadromous, pinnae often bending and/or curving towards the tip of the frond; pinnules lower innermost pinnule of the lowest pinnae large, resembling perhaps the third pinna above; costae grooves above continuous from rachis to costae; margins serrate; veins free, simple or forked, directed to notches.
Sori: round, in 1 row between midrib and margin, indusium: ovate, transparent, beneath sorus on midrib side, sporangia: black, maturity: midsummer to late summer.
Dimensionality: just above the basal pinna pair, the rachis curves over to hold the blade horizontally.
Culture Habitat: calcareous wet woods or along water courses, or in subalpine-arctic Salix communities. Distribution: boreal or subalpine Northern Hemisphere, never abundant. Hardy to -40°C, USDA Zone 2, requires a cool summer.
Distinctive Characteristics Elegant is a term that pops up in many descriptions. Certainly very lacy, evocative of Gymnocarpium in blade form and horizontal position. The only not-very-nice thing about it is the poisonous hydrocyannic acid emitted by bruised fronds. Perhaps not in cultivation, but impossible to omit.
Polypodium montanum Lamarck
Cystopteris montana
Cystopteris montana. top:segment with sori and glandular hairs on costa, left: stips scales, right: two pinnules closest to rachis.  Illustration from Scandinavian Ferns by Benjamin Øllgaard and Kirsten Tind, Rhodos, 1993.
Compare to There are a number of thrice+ divided, small ferns, but all are of a clumping habit. Gymnocarpium species are not quite as divided, but do possess the running habit and dimensionality of this plant; Gymnocarpium, however, has black stipes, lacks indusia.
Cystopteris montana
Cystopteris montana. a) frond, highly dissected; b) fertile pinnule or segment with veins ending in the notches.  Illustration by V. Fulford from Ferns and Fern Allies of Canada, William J. Cody and Donald M. Britton, 1989, © Agriculture Canada, used with permission.
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