Myriopteris gracillima, formerly known as Cheilanthes gracillima, is a species of lip fern known by the common name lace lip fern. It is native to western North America, where it grows in rocky habitat from British Columbia to California to Montana.[2][3]
Myriopteris gracillima growing in situ on basalt in the lower Columbia River gorge, WashingtonMyriopteris gracillima abaxial (lower) leaf surface, showing false indusium and narrow hair-like scalesMyriopteris gracillima leaf curled in response to drought
Leaf bases are closely spaced along the rhizome,[4][5] which is 4 to 8 millimeters (0.2 to 0.3in) in diameter.[4] It is ascending and branches.[6] It bears brown[4] to light brown[5] scales, sometimes uniformly colored[4] or with a darker, poorly defined stripe in the center, which may sometimes be red-brown.[5] They are linear-lanceolate in shape, straight or tightly twisted,[4]entire (lacking teeth) at the edges,[6] and only loosely appressed (pressed against the surface of the rhizome). The scales are not shed with age.[4]
The fronds arise from the rhizome in clusters; they do not unfold as fiddleheads like typical ferns (noncircinate vernation). When mature, they are 5 to 25 centimeters (2.0 to 9.8in) in length[4] (or even up to 30 centimeters (12in))[5] and 1 to 2 centimeters (0.4 to 0.8in) (or even up to 3 centimeters (1in)) wide.[5] The stipe (the stalk of the leaf below the blade) is 2.5 to 14 centimeters (0.98 to 5.5in) long[6] and about 1 millimeter (0.04in) wide,[5] rounded on the upper surface, and dark brown[4] or medium brown to purplish-black in color.[6] It bears a few scales,[6] which are linear-lanceolate and ciliate at the base,[5] pale and uniformly colored.[6]
The leaf blades are linear-oblong[4][5] or elliptic-lanceolate[6] in shape, about 3 to 5times longer than wide.[5] They are typically 3 to 10 centimeters (1 to 4in) long[6] and 0.6 to 2.5 centimeters (0.24 to 0.98in) wide.[4][6] The blade is usually bipinnate (cut into pinnae and pinnules) to tripinnate (cut into pinnae, pinnules, and pinnulets) at the base.[4][5][6] The rachis (leaf axis) is rounded on the upper side and bears a few linear scales.[4][5]
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 comparable in size than the pair just above them. The upper surfaces of the costae (pinna axes) are green for most of their length.[4]
Myriopteris gracillima is a small fern with dark green leaves up to about 25cm (10in) long that arise from a short creeping ground stem (rhizome), such that plants often have an elongated base, for example creeping along a rock crevice. Each frond is intricately divided into segments made up of pairs of smaller segments which are oval in shape and oblong beadlike, with their edges rolled under, giving it a somewhat succulent appearance. They are also quite hairy and scaly, mostly on the underside of the leaf and leaf mid-rib. The sori are located within rolled-under margins (false indusium) of each tiny leaf segment. It usually grows in sun in crevices in rock formations or sometimes in thin soil in and around rocks.[2]
More technical description adapted from Burke Herbarium:[7]Myriopteris gracillima is a lithophytic perennial, with leaves emerging from short creeping stems that are 4–8mm (0.2–0.3in) in diameter with narrow scales that are uniformly brown or with a weakly defined dark central stripe; the scales are straight to somewhat contorted, loosely appressed, and persistent. Leaves are 5–25cm (2–10in) long and 1–2.5cm (0.4–1in) wide and are born on a dark brown petiole. The leaf blade is linear-oblong and 2–3-pinnate at base. The rachis is rounded on the upper surface, with dispersed linear scales. Pinnae are not articulate, and the dark stalk color continues into the pinna base. Pinnae are usually equilateral, appearing slightly pubescent or glabrous on upper surface, with pinna midribs green on upper surface for the majority of length. Scales on the underside of the rachis are arranged in several rows, linear and truncate at base, inconspicuous, 0.1–0.4mm (0.004–0.02in) wide at most, loosely imbricate, not hiding the ultimate segments, and long-ciliate with cilia typically confined to the base. The ultimate pinna segments are oblong or rarely ovate and beadlike, 1.5–3mm (0.06–0.1in) at most. The leaf lower surface is densely covered with branched hairs and small ciliate scales. The leaf upper surface has dispersed and branched hairs, which tend to be shed as the leaf ages.[7]
Distribution and habitat
M.gracillima is native to mountains in western North America, ranging from British Columbia to California and southern Nevada.[8] It is absent in lower elevation dry inland areas such as the shrub-steppe of central Washington and Oregon and the central valley of California, but is present in the Rocky Mountains in British Columbia, Idaho, western Montana, northeastern Utah, and Nevada. It is also found at low elevation in the Columbia River gorge only in the region where it transects the Cascade Mountain range,[7][2] presumably because of higher precipitation.
M.gracillima grows primarily in sunny exposures in rock crevices with little or no soil.[7][2]
Ecology
Like many cheilanthoid ferns, M.gracillima tolerates desiccation well. During an extended dry period leaves curl and expose their hairy abaxial (lower) surface, presumably to reduce water loss. The leaves uncurl and green up when moisture returns.
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 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. One of these was C.gracillima, which thus became Myriopteris gracillima.[12]
In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H.gracillima, as part of a program to consolidate the cheilanthoid ferns into that genus.[13]
Members of the genus Cheilanthes as historically defined (which includes Myriopteris) are commonly known as "lip ferns" due to the lip-like (false) indusium formed by the leaf margins curling over the sori.[14] This species is commonly known as lace lip fern or lace fern.[4][6][15]
Myriopteris gracillima can be cultivated, and should be grown under high light in well-drained garden soil with sand. The soil should be moist-dry[15] and subacid.[6]
↑ Grusz, A. L., M. D. Windham, and K. M. Pryer. 2009. Deciphering the origins of apomictic polyploids in the Cheilanthes yavapensis complex (Pteridaceae). American Journal of Botany 96: 1636–1645
Short, Emma; George, Alex (2013). A Primer of Botanical Latin with Vocabulary. Cambridge, England: Cambridge University Press. ISBN978-1-107-69375-3.
Windham, Michael D.; Rabe, Eric W. (1993). "Cheilanthes gracillima". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico. Vol.2: Pteridophytes and Gymnosperms. New York and Oxford: Oxford University Press. Retrieved July 22, 2025.
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