Cystopteris Bernh.
Family: Dryopteridaceae
Bladder Fern
Cystopteris image
Robert W. Freckmann  

Key to Wisconsin Cystopteris

    • 1a.Blades triangular, widest at or near base, attenuate at apex; bulblets often present on upper part of rachis; most or all veins ending in tiny notches; small gland-tipped hairs usually present on rachis and indusia (except in C. tennesseensis); plants often on calcareous rocks 2

    • 1b.Blades ovate to narrowly lanceolate or elliptical, widest near middle, usually acute at apex; bulblets not produced; most or all veins ending in teeth (except many ending in notches in C. tenuis); tiny gland-tipped hairs lacking; plants often growing on forest soil or cliff faces 4

    • 2a.Most blades (except those emerging in spring) narrowly triangular, apex long-attenuate, often bearing globose bulblets; young petioles reddish; all veins ending in notches between lobes C. bulbifera

    • 2b.Blades triangular to narrowly ovate, apex short-attenuate, often with a few deformed bulblets; petioles brown to yellow-green; some veins ending in teeth 3

    • 3a.Blades narrowly ovate to lanceolate, the longest pinnae usually third or fourth above the base; gland-tipped hairs sparse; scales on rhizome dark brown C. laurentiana

    • 3b.Blades narrowly triangular, widest at the lowest or second lowest pair of pinnae; gland tipped hairs usually lacking; scales on rhizome tan C. tennesseensis

    • 4a.Stems protruding 1--4 cm beyond the leaves, covered with golden hairs; petioles pale green to straw-colored at base; usually growing on forest soil C. protrusa

    • 4b.Stems scarcely protruding beyond leaves, lacking hairs; petioles brown at the base; often growing on cliff faces 5

    • 5a.Pinnae with shallow rounded teeth; pinnules of lowest pinnae often cuneate at base; many veins ending in notches; pinnae often at acute angle to rachis and curved toward apex C. tenuis

    • 5b.Pinnae with sharp teeth; pinnules of lowest pinnae rounded to truncate at base; nearly all veins ending in pointed teeth; pinnae perpendicular to rachis and not curved toward apex C. fragilis

Diploid species are concentrated in North America and often hybridize when they occur together. Hybrids are usually sterile and have shriveled, malformed spores. Several species pairs have produced fertile allopolyploid derivatives. A complex genus, the subject of several taxonomic revisions.
Species within Green Lake County 2016