Southwestern False Cloak Fern

The rhizome is short and horizontal, with leaves closely spaced. It bears thin linear to lanceolate brown to reddish-brown or chestnut-brown scales, of a uniform color and with entire (toothless) margins. The leaves range from 5 to 30 centimeters (2.0 to 12 in) long. The stipe (the stalk of the leaf, below the blade) is reddish-brown to black, rounded, without hairs or scales, except that a few scales like those of the rhizome may be present at the very base. It is 3 to 12 centimeters (1.2 to 4.7 in) long and 0.75 to 2 millimeters (0.030 to 0.079 in) in diameter, making up about one-half to one-third of the total length of the leaf. The leaf blades are 2.5 to 11 centimeters (0.98 to 4.3 in) long. They vary from narrowly to broadly deltate (triangular) in shape, and ranges from tripinnate (cut into pinnae, pinnules and pinnulets) to pentapinnate at the base, where it is most divided. The rachis (leaf axis) is rounded or slightly flattened and hairless above, straight or slightly flexuous (zig-zagging), and dark in color, as are the axes of the leaf segments. The color continues into the base of the leaf segments, without a distinct joint. From 6 to 12 pairs of pinnae are present, gradually narrowing at their tips and generally widest at their bases. Leaf segments are numerous and closely spaced, small, elliptic to ovate or roundish to oblong in shape. …

Argyrochosma limitanea is known in the United States from San Bernardino County, California, east through Arizona, New Mexico, southern Utah and Colorado, and Trans-Pecos Texas, and south into northern Mexico, extending as far southeast as Hidalgo. A. limitanea subsp. limitanea ranges from California through Utah and Colorado and into Mexico only in Sonora and Chihuahua. A. limitanea subsp. mexicana has a more easterly range, from Arizona through Texas and in Mexico from Chihuahua and Sinaloa east. Both subspecies grow on rocky slopes and cliffs, composed of either calcareous or igneous rocks, although A. limitanea subsp. mexicana shows a greater preference for calcareous substrates in Mexico. A. limitanea subsp. limitanea is found at an altitude from 800 to 2,300 meters (2,600 to 7,500 ft), while A. limitanea subsp. mexicana, growing in the mountains, occurs from 1,500 to 2,500 meters (4,900 to 8,200 ft).

The white farina differs in chemistry among the two varieties. In A. limitanea var. mexicana, the principal component of the farina is 2',6'-dihydroxy-4'-methoxydihydrochalcone. A number of methoxy-substituted flavonoids were isolated as minor constituents: apigenin 7-methyl ether, apigenin 4'-methyl ether, apigenin 4',7-dimethyl ether, galangin 3,7-dimethyl ether, kaempferol 3,7-dimethyl ether, kaempferol 3,4',7-trimethyl ether, quercetin 3,4'7-trimethyl ether, quercetin 3,3',4'7-tetramethyl ether, pinocembrin, naringenin 7-methyl ether, eriodictyol 4',7-dimethyl ether and eriodictyol 3',4',7-trimethyl ether. A. limitanea var. mexicana also contains notholaenic acid, while A. limitanea var. limitanea contains isonotholaenic acid, like A. chilensis, A. dealbata, and A. nivea.