Argyrochosma pallens

Argyrochosma pallens is a medium-sized epipetric fern. The rhizome may be upright or decumbent (horizontal, curving upward at the tip). It bears linear to lanceolate scales 2 to 5 millimeters (0.08 to 0.2 in) long that terminate in a fine hair, of a uniform reddish-brown color, with entire (toothless) margins. The fronds arise in clumps from the rhizome. From base to tip of leaf, they are up to 20 centimeters (7.9 in) long. Of this length, from 20% to 33% is made up by the stipe (the stalk of the leaf, below the blade). Both stipe and rachis (leaf axis) are round and chestnut-brown, bearing farina (powder) and a scattering of narrow linear or slightly lance-shaped scales 1 to 2 millimeters (0.04 to 0.08 in) of the same color. The leaf blades are 1 to 2 centimeters (0.4 to 0.8 in) wide and narrowly oblong. They are bipinnate-pinnatifid to tripinnate (cut into pinnae and pinnules that are either deeply lobed or cut into pinnulets). The leaf segments are oblong to broadly deltate-ovate, and are obtuse (blunt) at the tip. The brown color of the axes does pass somewhat into the leaf tissue, but not strikingly so. The upper side of the leaf is covered with a scattering of white farina, which thickly covers the under side. The sori lie along the veins, forming a band near the perimeter of the leaf segment only 0.5 to 1 millimeter (0.02 to 0.04 in) wide. …

Argyrochosma pallens is endemic to Mexico, occurring from Chihuahua southeast through central Mexico as far as Oaxaca. It is found on cliffs and ledges, usually limestone ones, particularly within the spiny matorral, at altitudes from 1,500 to 2,920 meters (4,920 to 9,580 ft).