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