Cystopteris fragilis is a small fern, with fronds to 40
cm long, but often about half that size. In some earlier treatments
Cystopteris fragilis was interpreted in a broader sense
to include C. laurentiana, C. tennesseensis, C.
protrusas and C. tenuis as varieties. See steps
60-64 in the key to distinguish the species, or refer to the
Flora of North America, vol. 2 for a more thorough treatment of
this difficult group of species.
Cystopteris fragilis is broadly distributed across northern
North America, south to California, New Mexico, northern Illinois,
New York and Connecticut. In Wisconsin it is known from scattered
locations, with the greatest incidence in Door County and near
Lake Superior. It prefers rocks as a substrate.