# Myriopteris lindheimeri

Myriopteris lindheimeri, formerly known as Cheilanthes lindheimeri, is a species of fern in the Pteridaceae family (subfamily Cheilanthoideae) with the common name fairy swords.

## Description

Myriopteris lindheimeri grows in dense colonies from a long creeping rhizome with brown scales. Leaves are generally lanceolate and 7–30 cm long and 2–5 cm wide with a dark brown petiole. The leaf blade is 4-pinnate at the base, grayish or silvery green on top and covered with rusty brown wooly hairs below. The rachis has scattered linear-lanceolate scales and sparse hairs. Ultimate leaf segments are round to slightly oblong, beadlike, up to 0.7–1 mm in diameter. The tops of the leaves typically have a distinctive silvery green tone.

## Range and habitat

Myriopteris lindheimeri is native to southwestern United States and northern Mexico. It grows on rocky slopes and ledges, on a variety of acidic to mildly basic substrates, at elevations from 200 to 2500 m.

## Taxonomy

Myriopteris lindheimeri was first described by Sir William Jackson Hooker in 1852, as Cheilanthes lindheimeri, based on material collected by Ferdinand Lindheimer in western Texas in 1847. The epithet presumably honors Lindheimer. While Hooker accepted the species within a broad circumscription of Cheilanthes, a classification followed by most botanists through the 20th century, his contemporary Antoine Laurent Apollinaire Fée preferred to separate some species into a new genus, Myriopteris based on characters of the false indusia and sori. Following this classification, John Smith transferred C. lindheimeri there as Myriopteris lindheimeri in 1854.
In 1891, John Gilbert Baker described a species he called Cheilanthes albida, based on the specimen Charles Christopher Parry & Edward Palmer 999, collected by those two botanists in Central Mexico. He did not explain the epithet albida, meaning "whitish", but he described it as being "densely white-hairy on both surfaces". A subsequent examination of the type specimen revealed it to be the same as C. lindheimeri.
By a strict application of the principle of priority, Oliver Atkins Farwell transferred the species to the genus Allosorus as Allosorus lindheimeri in 1931, that genus having been published before Cheilanthes. Farwell's name was rendered unnecessary when Cheilanthes was conserved over Allosorus in the Paris Code published in 1956.
The development of molecular phylogenetic methods showed that the traditional circumscription of Cheilanthes is polyphyletic. Convergent evolution in arid environments is thought to be responsible for widespread homoplasy in the morphological characters traditionally used to classify it and the segregate genera, such as Myriopteris, that have sometimes been recognized. On the basis of molecular evidence, Amanda Grusz and Michael D. Windham revived the genus Myriopteris in 2013 for a group of species formerly placed in Cheilanthes, including Myriopteris lindheimeri.
In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. lindheimeri, as part of a program to consolidate the cheilanthoid ferns into that genus.
Myriopteris lindheimeri is an apogamous (asexually reproducing) triploid of unknown parentage. Based on plastid DNA sequence, Myriopteris lindheimeri is part of Myriopteris clade C (covillei clade) and is very closely related to Myriopteris yavapensis. It is occasionally misidentified as Myriopteris wootonii.