Myriopteris gracilis, commonly known as slender lip fern or Fee's lip fern, is a small fern native to western North America, with a few scattered populations in the east. Its leaves grow in clusters and are dissected into beadlike segments, pale green with pale hairs covering the underside. One of the cheilanthoid lip ferns, it was usually classified in the genus Cheilanthes as Cheilanthes feei until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It grows in rocky habitats, usually over limestone.
Description
The rhizomes are short with closely-spaced leaf bases, measuring 2 to 3 millimeters (0.08 to 0.1 in) or 4 to 8 millimeters (0.2 to 0.3 in) in diameter, upright or ascending rather than horizontal, and branching. The rhizome bears persistent linear-lanceolate scales, slightly erose (jagged) at the margins, slightly twisted, and loosely appressed (pressed against the surface of the rhizome). They are brown, light to red-brown, orange-brown, or pale brown in color, mostly with a blackish or dark central stripe. The fronds arise from the rhizome in clusters, reaching a size from 4 to 20 centimeters (2 to 8 in) long and 1.5 to 3 centimeters (0.59 to 1.2 in) wide. They emerge as fiddleheads (circinate vernation). The stipe (the stalk of the leaf below the blade) makes up about one-half to one-third of the total length of the frond. It is 2 to 8 centimeters (0.8 to 3 in) long and about 1 millimeter (0.04 in) wide, rounded on the upper surface, and generally dark brown to black in color, or reddish-brown to blackish. It bears straight multicellular hairs less than 2 millimeters (0.08 in) long. They are pale to tan in color with orange constrictions. The leaf blades are linear-oblong to lanceolate or linear-lanceolate in overall shape, typically 2.5 to 7 centimeters (0.98 to 2.8 in) long (occasionally as long as 10 centimeters (3.9 in)) and 1 to 3 centimeters (0.4 to 1 in) wide. They are obtuse to truncate at the base and acute at the tip. They are typically bipinnate-pinnatifid (cut into pinnae and lobed pinnules) to tripinnate (cut into pinnae, pinnules, and pinnulets) at the base. The rachis (leaf axis) is similar in morphology to the stipe, which it extends: rounded above, and densely covered with uniform hairs. Scales are absent. There are typically 3 to 10 pairs of pinnae, which are narrowly to broadly deltate in shape. At the base of each pinna, the dark color of the costa continues into the pinna base; there is no distinct joint between stalk and leaf. The basal pinnae are slightly smaller than the pair just above them. The upper surfaces of the costae (pinna axes) are brown for most of their length. The pinnulets are round or slightly oblong in shape with a beadlike appearance, the larger ones measuring about 1 to 3 millimeters (0.04 to 0.1 in) across. The blade tissue is pale green. The upper surface of the leaf has at most a sparse covering of hairs and can be glabrescent (almost free of hair), while they form a dense covering on the lower surface. The leaf hairs are long, segmented, white to brown or reddish-brown, curved but not intertwined. On fertile fronds, the edge of the leaf folds under to form a false indusium from 0.05 to 0.25 mm wide. The tissue of the false indusia is only weakly differentiated from that of the rest of the leaf blade. Beneath the false indusia, the sori are more or less continuous around the margins of the beadlike segments. They tend to be hidden more by the dense hairs than by the folded margin. Each sporangium contains 32 spores. Individual sporophytes are apogamous triploids, with a chromosome number of 2n = 90. It may be confused with M. parryi in California, due to the presence of hairs, but the hairs are thinner and sparser in M. gracilis and its ultimate segments are smaller.
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