This is a fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

, P. atropurpurea, commonly known as purple-stem cliffbrake or just purple cliffbrake. Brake is an old word for fern, related to the word bracken

Bracken

Bracken are several species of large, coarse ferns of the genus Pteridium. Ferns are vascular plants that have alternating generations, large plants that produce spores and small plants that produce sex cells . Brackens are in the family Dennstaedtiaceae, which are noted for their large, highly...

. Like many other members of the Pteridaceae

Pteridaceae

Pteridaceae is a large family of ferns in the order Pteridales. Members of the family have creeping or erect rhizomes and are mostly terrestrial or epipetric...

, it is a rock plant, needing a calcareous substrate.

P. atropurpurea is an apogamous autotriploid, with 3n=87 (actual base number, n=29), and is one of the historical parents of the hybrid species complex, Pellaea glabella

Pellaea glabella

Pellaea glabella is the smooth cliffbrake. For much of pteridological history, it was regarded as a reduced form or variety of Pellaea atropurpurea. P. glabella is known to exist in two cryptic species, one diploid and one tetraploid. The diploid reproduces sexually, while the tetraploid is...

. Apogamy, or the ability to reproduce non-sexually, is common among rock ferns in the Pteridaceae

Pteridaceae

Pteridaceae is a large family of ferns in the order Pteridales. Members of the family have creeping or erect rhizomes and are mostly terrestrial or epipetric...

.

This cliffbrake can be grown in a rock garden or potted with care.

Characteristics

This fern produces clumps of widely arching fronds. The stipe

Stipe (botany)

In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described....

 and rachis

Rachis

Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...

 of the blade are purple, while the blade itself has a blue-gray tinge to it. The upper pinnae are long, narrow, and undivided, while the lower ones are divided into 3-15 pinnules. The pinnae are, for the most part, opposite. Fertile fronds are longer and more heavily divided. They produce sori, which lack a true indusium, within the inrolled margins of the pinnae.

This plant may be distinguished from the similar Pellaea glabella

Pellaea glabella

Pellaea glabella is the smooth cliffbrake. For much of pteridological history, it was regarded as a reduced form or variety of Pellaea atropurpurea. P. glabella is known to exist in two cryptic species, one diploid and one tetraploid. The diploid reproduces sexually, while the tetraploid is...

by its hairier nature and larger form.

Ecology

Pellaea atropurpurea grows in the crevices of dry limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 cliffs, rocky slopes, and mortared walls. It is endangered in Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

, Iowa

Iowa

Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

, and Rhode Island

Rhode Island

The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...

.