Myriopteris covillei

Myriopteris covillei, formerly known as Cheilanthes covillei, is a species of cheilanthoid fern known by the common name Coville's lip fern. Coville's lip fern is native to the southwestern United States and Mexico.

Description
Leaf bases are closely spaced along the rhizome, which is typically 2 to 4 mm in diameter. It is covered with persistent scales about 2 mm long, which are linear to narrowly lanceolate, straight or slightly twisted, and tightly appressed (pressed against the surface of the rhizome). They are a uniform dark brown to black in color, or in some cases have paler, narrow margins of a light brown color, and lack marginal teeth.

The fronds spring up in clusters; they do not unfold as fiddleheads like typical ferns (noncircinate vernation). When mature, they are 5 to 30 cm long. The stipe (the stalk of the leaf below the blade) is 3 to 17 cm long and less than 2 mm wide, rounded on the upper surface, dark brown to dark reddish-brown in color. It is covered with white to red-brown, lanceolate to linear scales.

The leaf blades are lanceolate to ovate-deltate in shape, typically 1.5 to 5 cm or even 6 cm wide and tripinnate to tetrapinnate (cut into pinnae, pinnules, pinnulets, and sometimes into divisions of pinnulets) at the base. The rachis (leaf axis) is rounded, rather than grooved, on its upper surface, dark in color, with some scales but no hairs. No distinct joint is present where the pinnae attach to the rachis, the dark color of the latter continuing into the base of the costa (pinna axis). Each pinna is equilateral in shape, and the lowest pair of pinnae is not significantly enlarged compared to the others. Aside from the dark base, the upper surface of the costae is green along much of their length. The lower surface of the costae is covered in conspicuous scales. These are ovate-lanceolate in shape, and deeply cordate (notched at the base to appear heart-shaped). The largest scales are 0.4 to 1.5 mm wide. The scales overlap each other, and sometimes conceal the final subdivisions of the leaf from below. Only the basal lobes of the scales are ciliate.

This fern has dark to medium green leaves (fronds) which may be up to 4-pinnate (made up of leaflets that subdivide up to 3 times), such that the leaflets are layered with overlapping rounded segments. The leaves as a whole have a bumpy, cobbled look when viewed from above. The edges of the leaflets are curled under (forming a false indusium) and their undersides have wide scales which are lengthened outgrowths of the epidermis. Tucked under the scales and false indusium are the sporangia, which make the spores. Myriopteris covillei can be distinguished from its very similar relative Myriopteris intertexta by the scales on the underside of the leaflets. These scales are up to 3 mm wide at their base in M. covillei, giving them an elongated triangular papery appearance, whereas those of M. intertexta are 1 mm wide, appearing more like a flattened thread.



Range and Habitat
Coville's lip fern is native to California, Baja California, Arizona, Oregon, and Utah.

It grows in rocky crevices in the mountains and foothills. In California it is found in chaparral, yellow pine forest, pinyon-juniper woodland, and Joshua tree woodland habitats.

Taxonomy
Based on plastid DNA sequence, Myriopteris covillei is part of Myriopteris clade C (covillei clade) and is most closely related to Myriopteris clevelandii and Myriopteris gracillima. In addition, Myriopteris covillei is one of the parents of the fertile allotetraploid Myriopteris intertexta.

Ecology and conservation
While globally apprently secure (G4), M. covillei is threatened in the northern part of its range. NatureServe considers it to be critically imperiled in Oregon, imperiled in Utah, and vulnerable in Nevada.