Cheilanthes
Syn. Fil. 126. 1806.
Plants usually on rock. Stems compact to long-creeping, ascending to horizontal, usually branched; scales brown to black or often bicolored with dark central stripe and lighter margins, linear-subulate to ovate-lanceolate, margins entire or denticulate. Leaves monomorphic, clustered to widely scattered, 4–60 cm. Petiole brown to black or straw-colored, rounded, flattened, or with single longitudinal groove adaxially, pubescent, scaly, or glabrous, with a single vascular bundle. Blade linear-oblong to lanceolate, ovate, or elongate-pentagonal, pinnate-pinnatifid to 4-pinnate at base, leathery or rarely somewhat herbaceous, abaxially pubescent and/or scaly, rarely glabrous, adaxially pubescent to glabrous, dull, not striate; rachis straight. Ultimate segments of blade stalked or sessile, usually free from costae, round to elongate or spatulate, usually less than 4 mm wide, base rounded, truncate, or cuneate; stalks (when present) often lustrous and dark colored; segment margins usually recurved to form confluent, poorly defined false indusia, extending entire length of segment or discontinuous on apical or lateral lobes. Veins of ultimate segments free or rarely anastomosing, pinnately branched and divergent distally. False indusia greenish to whitish, usually narrow, clearly marginal or rarely inframarginal, often concealing sporangia. Sporangia confined to submarginal vein tips or scattered along veins near segment margins, containing 64 or 32 spores, not intermixed with farina-producing glands. Spores brown to black or gray, rarely yellowish, tetrahedral-globose, rugose or cristate, lacking prominent equatorial ridge. Gametophytes glabrous. x = 30 (29 in Cheilanthes alabamensis complex).
Distribution
Mostly Western Hemisphere but a few in Europe, Asia, Africa, Pacific Islands, and Australia.
Discussion
Cheilanthes is by far the largest and most diverse genus of xeric-adapted ferns. In its classic circumscription, the genus has been notoriously difficult to distinguish from other cheilanthoid genera, especially Notholaena and Pellaea (R. M. Tryon and A. F. Tryon 1982). This has led some authors (e.g., J. T. Mickel 1979b) to abandon several of the segregate genera and greatly expand the number of species assigned to Cheilanthes. Taxonomic problems in this group have motivated an ongoing series of biosystematic studies that offer hope for a stable classification through the identification of natural, monophyletic groups. The circumscription of Cheilanthes has been clarified recently by a redefinition of Notholaena and the transfer of several species (e.g., N. parryi, N. newberryi, and N. aurea) to Cheilanthes (R. M. Tryon and A. F. Tryon 1982). The boundaries of the genus have been further sharpened by the recognition of Aspidotis (A. R. Smith 1975), Argyrochosma (M. D. Windham 1987), and Astrolepis (D. M. Benham and M. D. Windham 1992) as distinct genera. Despite these efforts, Cheilanthes remains a very heterogeneous (and probably polyphyletic) genus in need of further critical study.
The circumscription of Cheilanthes used here closely parallels that proposed by T. Reeves (1979), who recognized four New World subgenera and a small group of species of uncertain placement. Among the North American species, C. pringlei and C. wrightii belong to the latter group, and C. arizonica is the sole representative of subgenus Othonoloma Link ex C. Christensen. The subgenus that Reeves called the Cheilanthes alabamensis group is represented in North America by C. aemula, C. alabamensis, C. microphylla, and C. horridula. It differs from other members of the genus in a number of critical features (e.g., blade indument, sporangial distribution, and chromosome base number) that suggest a relationship to the genus Pellaea. Although the group is somewhat anomalous in Cheilanthes, inclusion of the C. alabamensis complex in Pellaea (e.g., R. Cranfill 1980) would make that genus polyphyletic. The group is maintained here in Cheilanthes with the recognition that it may constitute a natural group worthy of consideration as a distinct genus.
The remaining 21 North American species of Cheilanthes are almost evenly divided between subgenus Physapteris (C. Presl) Baker in Hooker & Baker and subgenus Cheilanthes. The former subgenus is characterized by T. Reeves (1979) as having noncircinate vernation, usually scaly blades with small, beadlike ultimate segments, and hairs with cell walls that fit together in "tongue and groove" fashion. Species of subgenus Cheilanthes typically have circinate vernation, nonscaly blades with larger ultimate segments, and hairs with straight cross-walls. Despite the consistency of these differences, the two groups are closely related and linked by occasional intersubgeneric hybridization between C. covillei (subg. Physapteris) and C. parryi and C. newberryi (subg. Cheilanthes).
Species ca. 150 (28 in the flora).
Selected References
Lower Taxa
Key
| 1 | Costae with multiseriate scales abaxially (narrow and inconspicuous in Cheilanthes gracillima and C. tomentosa), intermixed with hairs in some species; vernation noncircinate, expanding leaves hooked but not coiled at tips. | > 2 |
| 1 | Costae lacking multiseriate scales, pubescent or glabrous; vernation circinate or noncircinate, expanding leaves tightly coiled at tip in most species. | > 14 |
| 2 | Rachises and distal portion of petioles grooved adaxially; ultimate segments spatulate; sori discontinuous, confined to apical and lateral lobes. | Cheilanthes pringlei |
| 2 | Rachises and petioles rounded or slightly flattened adaxially; ultimate segments round, elliptic, or oblong; sori ± continuous around segment margins. | > 3 |
| 3 | Ultimate segments scabrous, covered with stiff, usually pustulose hairs; fertile ultimate segments narrowly elliptic, the largest 3-5 mm. | Cheilanthes horridula |
| 3 | Ultimate segments smooth to touch, lacking stiff, pustulose hairs; fertile ultimate segments round to somewhat elliptic, the largest less than 3 mm. | > 4 |
| 4 | Costal scales linear, inconspicuous, the largest 0.1-0.4 mm wide. | > 5 |
| 4 | Costal scales lanceolate to ovate, conspicuous, the largest 0.4-1.5 mm wide. | > 6 |
| 5 | Ultimate segments pubescent adaxially with fine, unbranched hairs; costal scale margins entire; blades 3-pinnate for most of length. | Cheilanthes tomentosa |
| 5 | Ultimate segments glabrescent adaxially or bearing scattered, branched hairs; costal scale margins ciliate at base; blades predominantly 2-pinnate (occasionally 3-pinnate at base). | Cheilanthes gracillima |
| 6 | Costal scale margins entire to erose or denticulate (rarely with 1 or 2 cilia in Cheilanthes eatonii). | > 7 |
| 6 | Costal scale margins ciliate, especially near base (inconspicuously so in C. covillei). | > 9 |
| 7 | Ultimate segments completely glabrous adaxially; stems long-creeping, 1-3 mm diam.; stem scales mostly concolored, brown. | Cheilanthes fendleri |
| 7 | Ultimate segments densely to sparsely pubescent adaxially; stems compact, usually 5-10 mm diam.; stem scales mostly bicolored with dark, well-defined central stripe and light brown margins. | > 8 |
| 8 | Ultimate segments densely tomentose with fine hairs abaxially; costal scales usually linear-lanceolate, loosely imbricate, not concealing ultimate segments. | Cheilanthes eatonii |
| 8 | Ultimate segments nearly glabrous abaxially except for a few coarse hairs; costal scales ovate-lanceolate, strongly imbricate, usually concealing ultimate segments. | Cheilanthes villosa |
| 9 | Costal scales ovate-lanceolate with deeply cordate bases, basal lobes usually overlapping to close sinus, scales usually ciliate only in proximal 1/2; sporangia containing 64 spores; stems usually short-creeping, leaves clustered (separated to 10 mm in C. clevelandii). | > 10 |
| 9 | Costal scales lanceolate with truncate or subcordate bases, basal lobes (when present) not overlapping, scales often ciliate throughout; sporangia containing 32 spores; stems usually long-creeping, leaves scattered. | > 12 |
| 10 | Costal scales ciliate on basal lobes only, thus often appearing to lack cilia; ultimate segments glabrous or with a few entire to weakly ciliate scales abaxially, lacking branched hairs; stem scales usually dark brown or black throughout, rarely with narrow, light brown margins. | Cheilanthes covillei |
| 10 | Costal scales conspicuously ciliate over most of proximal 1/2; ultimate segments pubescent abaxially with branched hairs and ciliate scales; stem scales usually bicolored. | > 11 |
| 11 | Ultimate segments oblong to ovate, sparsely pubescent adaxially (often glabrescent when mature); stem scales linear-lanceolate with pale, narrow margins much narrower than width of dark, central stripe. | Cheilanthes intertexta |
| 11 | Ultimate segments round to subcordate, glabrous adaxially; stem scales lanceolate with pale, broad margins approaching width of dark, central stripe. | Cheilanthes clevelandii |
| 12 | Pinnae appearing densely tomentose adaxially; costal scales with fine, curly cilia forming entangled mass; ultimate segments minute, 0.5-1 mm. | Cheilanthes lindheimeri |
| 12 | Pinnae appearing glabrous or sparsely pubescent adaxially; costal scales with coarse cilia that are not strongly entangled; ultimate segments larger, at least some 1-3 mm. | > 13 |
| 13 | Pinnae appearing glabrous adaxially; costal scales often ciliate only in proximal 1/2; stem scales usually brown, concolored, loosely appressed and deciduous on older portions of stem. | Cheilanthes wootonii |
| 13 | Pinnae appearing sparsely pubescent adaxially; costal scales usually ciliate entire length; stem scales dark brown, often bicolored, usually strongly appressed and persistent. | Cheilanthes yavapensis |
| 14 | Rachises and pinnae essentially glabrous; petioles adaxially grooved for most of length. | > 15 |
| 14 | Rachises (and often pinnae) pubescent or glandular; petioles rounded, flattened, or slightly grooved distally but never grooved below middle adaxially. | > 16 |
| 15 | Basal pinnae conspicuously larger than adjacent pair; stems compact, usually 4-8 mm diam.; ultimate segments with scattered reddish glands abaxially. | Cheilanthes arizonica |
| 15 | Basal pinnae slightly smaller than or equal to adjacent pair; stems long-creeping, 1-3 mm diam.; ultimate segments lacking reddish glands abaxially. | Cheilanthes wrightii |
| 16 | Rachis pubescence dimorphic, abaxially sparsely hirsute with long, divergent hairs, adaxially densely covered with tortuous, appressed hairs; ultimate segments sparsely and inconspicuously pubescent abaxially, often appearing glabrous. | > 17 |
| 16 | Rachis pubescence monomorphic, hairs similar in form and density abaxially and adaxially; ultimate segments conspicuously pubescent or glandular abaxially. | > 19 |
| 17 | Basal pinnae inequilateral, proximal basiscopic pinnules conspicuously enlarged; blades ovate to deltate, 5-15 cm wide. | Cheilanthes aemula |
| 17 | Basal pinnae ± equilateral, proximal basiscopic pinnules not conspicuously enlarged; blades lanceolate to narrowly oblong, 1-7 cm wide. | > 18 |
| 18 | Costae green adaxially for most of length; most sporangia containing 32 spores; stems short-creeping to compact, usually 4-7 mm diam. | Cheilanthes alabamensis |
| 18 | Costae black adaxially for most of length; most sporangia containing 64 spores; stems long-creeping, 1-3 mm diam. | Cheilanthes microphylla |
| 19 | False indusia inframarginal, strongly differentiated, 0.25-0.5 mm wide, forming pouch with constricted aperture abaxially on beadlike ultimate segments; ultimate segments nearly glabrous adaxially. | Cheilanthes lendigera |
| 19 | False indusia marginal, weakly differentiated or absent, 0-0.25 mm wide, not forming pouch with constricted aperture abaxially on ultimate segments; ultimate segments pubescent or glandular adaxially (glabrescent in older leaves of Cheilanthes feei). | > 20 |
| 20 | Blades pinnate-pinnatifid throughout; pinnae clearly articulate, dark color of stalk stopping abruptly at swollen, hirsute node. | Cheilanthes bonariensis |
| 20 | Blades 2-4-pinnate at base; pinnae not articulate, color of stalk continuing into pinna base. | > 21 |
| 21 | Blades elongate-pentagonal, usually 5-10 cm wide; basal pinnae conspicuously larger than adjacent pair, inequilateral, proximal basiscopic pinnules greatly enlarged. | > 22 |
| 21 | Blades linear to ovate-lanceolate, usually 1-5 cm wide; basal pinnae about same size as adjacent pair, ± equilateral, proximal basiscopic pinnules not greatly enlarged. | > 23 |
| 22 | Petioles reddish purple to dark brown; ultimate segments resinous-sticky, covered with short, capitate glands. | Cheilanthes kaulfussii |
| 22 | Petioles straw-colored; ultimate segments not noticeably sticky, covered with long, noncapitate hairs. | Cheilanthes leucopoda |
| 23 | Ultimate segments with very fine, cobwebby hairs; stem scales uniformly black or dark brown, strongly appressed. | Cheilanthes newberryi |
| 23 | Ultimate segments bearing coarse hairs, not at all cobwebby; stem scales uniformly brown or bicolored, loosely appressed. | > 24 |
| 24 | Stem scales concolored, uniformly brown or slightly darker toward tip; rachises strongly flattened or shallowly grooved adaxially; costae green adaxially for most of length. | > 25 |
| 24 | At least some stem scales bicolored, darker toward center or base; rachises rounded or slightly flattened adaxially; costae brown adaxially for most of length. | > 26 |
| 25 | Ultimate segments conspicuously resinous-sticky, covered with short, capitate glands; stem scales strongly contorted. | Cheilanthes viscida |
| 25 | Ultimate segments not conspicuously sticky, covered with long, strongly flattened hairs; stem scales straight to slightly contorted. | Cheilanthes cooperae |
| 26 | Fertile ultimate segments nearly round, beadlike, 1-3 mm; sporangia containing 32 spores; blades 3-pinnate near base. | Cheilanthes feei |
| 26 | Fertile ultimate segments elongate, not beadlike, usually 3-5 mm; sporangia containing 64 spores; blades 2-pinnate-pinnatifid near base. | > 27 |
| 27 | Ultimate segments densely villous adaxially; many stem scales strongly bicolored with well-defined central stripe. | Cheilanthes parryi |
| 27 | Ultimate segments sparsely hirsute adaxially; most stem scales weakly bicolored with poorly defined central stripe. | Cheilanthes lanosa |