Cystopteris

Cystopteris is a genus of ferns in the family Cystopteridaceae. These are known generally as bladderferns or fragile ferns. They grow in temperate areas worldwide. This is a very diverse genus and within a species individuals can look quite different, especially in harsh environments where stress stunts their growth. They hybridize easily with each other and identifying an individual can be challenging. In general these are rhizomatous perennials which grow in rocks or soil. Their leaves are multiply pinnate, in that each leaflet is divided into smaller parts. The sori are usually rounded and covered in an inflated bladder-like indusium.

Species
Species include:
 * Cystopteris alpina
 * Cystopteris bulbifera - bulblet fern
 * Cystopteris chinensis (Ching) R.Wei & X.C.Zhang (syn. Cystoathyrium chinense Ching )
 * Cystopteris diaphana
 * Cystopteris dickieana - Dickie's bladderfern
 * Cystopteris douglasii - Douglas' bladderfern
 * Cystopteris fragilis - brittle bladderfern
 * Cystopteris laurentiana - St. Lawrence bladderfern
 * Cystopteris montana - mountain bladderfern
 * Cystopteris protrusa - lowland bladderfern
 * Cystopteris reevesiana - Reeves' bladderfern
 * Cystopteris tennesseensis - Tennessee bladderfern
 * Cystopteris tenuis - upland brittle fern
 * Cystopteris utahensis - Utah bladderfern

Hybrids
Cystopteris widely hybridizes internally. Its diploid parent species include:


 * C. bulbifera
 * C. "hemifragilis" (an undiscovered or extinct diploid)
 * C. protrusa
 * C. reevesiana

The hybrid species include:


 * C. fragilis (C. "hemifragilis" × C. reevesiana; allotetraploid)
 * C. laurentiana (C. bulbifera × C. fragilis; allohexaploid)
 * C. tennesseensis (C. bulbifera × C. protrusa; allotetraploid)
 * C. tenuis (C. "hemifragilis" × C. protrusa; allotetraploid)
 * C. utahensis (C. reevesiana × C. bulbifera; allotetraploid)

Non-species hybrids include:


 * Cystopteris × illinoensis (C. bulbifera × C. tenuis; allotriploid)
 * Cystopteris × wagneri (C. tennesseensis × C. tenuis; allo-allotetraploid)
 * Cystopteris fragilis × Cystopteris tenuis (allo-allotetraploid)
 * Cystopteris protrusa × Cystopteris tennesseensis (allotriploid)