Cystopteris protrusa
Encyclopedia
Cystopteris protrusa is a common fern of eastern North America
. Throughout much of its range, it is the most common Cystopteris. It is commonly known as the lowland brittle fern or lowland fragile fern. The specific name, protrusa, refers to the fact that the rhizome protrudes a short distance beyond the current year's fronds to form the following year's leaf buds. This protrusion is a positive diagnostic in the field. Sori are round and covered in a bladder-like indusium.
Unlike most species of this genus, this fern is exclusively terrestrial, often forming large, dense colonies. It is also largely a spring ephemeral. Some fronds may remain by late summer, but most have disappeared.
C. protrusa was originally considered only a variety of Cystopteris fragilis
. However, it is now known that this is a diploid species, while C. fragilis (ss) is a polyploid species of hybrid origin. C. protrusa is a parent of the hybrid species Cystopteris tennesseensis and Cystopteris tenuis
. Also see Cystopteris hybrid complex
.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Throughout much of its range, it is the most common Cystopteris. It is commonly known as the lowland brittle fern or lowland fragile fern. The specific name, protrusa, refers to the fact that the rhizome protrudes a short distance beyond the current year's fronds to form the following year's leaf buds. This protrusion is a positive diagnostic in the field. Sori are round and covered in a bladder-like indusium.
Unlike most species of this genus, this fern is exclusively terrestrial, often forming large, dense colonies. It is also largely a spring ephemeral. Some fronds may remain by late summer, but most have disappeared.
C. protrusa was originally considered only a variety of Cystopteris fragilis
Cystopteris fragilis
Cystopteris fragilis is a species of fern known by the common names brittle bladderfern and common fragile fern. It can be found worldwide, generally in shady, moist areas. The leaves are up to 30 or 40 centimeters long and are borne on fleshy petioles. Each leaf is divided into many pairs of...
. However, it is now known that this is a diploid species, while C. fragilis (ss) is a polyploid species of hybrid origin. C. protrusa is a parent of the hybrid species Cystopteris tennesseensis and Cystopteris tenuis
Cystopteris tenuis
Cystopteris tenuis is sometimes known as Mackay's bladder fern or Mackay's fragile fern. It was long considered to be a part of the superspecies for fragile ferns, as Cystopteris fragilis Bernh. var. mackayi Lawson....
. Also see Cystopteris hybrid complex
Cystopteris hybrid complex
-North American Cystopteris Hybrids:The diploid parent species within the genus include:*C. bulbifera*C. "hemifragilis" *C. protrusa*C. reevesianaThe hybrid species include:...
.