Cyclogramma

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 39-40

CYCLOGRAMMA

Cyclogramma Tagawa, Acta Phytotax. Geobot. 7:52. 1938.— Thelypteris subg. Cyclogramma (Tagawa) K. Iwats., Mem. Coll.Sci.Univ. Kyoto, ser. B, 31:26.1964.

— TYPE: Cyclogramma simulans (Ching) Tagawa [= Thelypteris simulans Ching ] = C. auriculata (J. Sm.) Ching

For additional synonymy, see Holttum (1971, 1982).

Etymology.— Gr. kyklos, circle + gramme, line. The sori are small, round, and in lines ( Stewart et al. 1983).

Plants terrestrial, small to medium-sized, evergreen; rhizomes short- to long-creeping, occasionally suberect ( C. auriculata ), mostly 3–5 mm diam.; fronds arching to erect, moderately sized to occasionally large, typically 35–130 (–220) cm, monomorphic, blades deeply pinnate-pinnatifid; stipes dull stramineous to brownish, blackened at bases, bearing basal scales and sparse to sometimes dense acicular and hooked hairs, the scales occasionally persistent distally ( C. squamaestipes ), even onto the rachis; stipe scales brown to blackish, ovate to lanceolate, bearing acicular hairs and sometimes also hooked hairs; blades herbaceous to chartaceous, drying dark green, olivaceous, or blackish ( Ching 1963), proximal pinnae not noticeably or only slightly shorter than more distal pinnae, or sometimes several pairs (1–5) abruptly reduced, if gradually shortened then becoming a series of hastate auricles; blade apex gradually reduced; proliferous buds absent; pinnae with costae grooved adaxially, incised to 0.5– 3 mm from costae, nearly symmetrical with segments spreading or slightly oblique and sometimes falcate, rounded at tips; margins entire, pinna bases sessile to short-petiolulate, truncate, acroscopic segment of greatly reduced pinnae often slightly elongate or auriculate; veins readily visible, free, simple or often forked, ending at margins of lobes just above sinuses, never united, sometimes with a raised non-vascularized keel abaxially just below sinuses ( C. auriculata ); aerophores at pinna bases at least swollen, greatly elongate in most species (0.5– 4 mm); indument abaxially of unicellular, hooked (hamate) hairs on all axes (rachis, costae, and costules), lacking costal scales, tissue between veins glabrous and sometimes of acicular and/or hooked hairs; indument adaxially of usually long (> 1 mm), stout, hyaline acicular hairs restricted mostly to costae, with fewer, shorter ones also sometimes present on costules, veins, and (less often) on laminar tissue; pustules absent; sori typically round and discrete, not elongate or confluent at maturity, lacking receptacular hairs, medial, inframedial, or subcostular, indusia absent; sporangia usually bearing hooked hairs on capsules like those of laminae but shorter, lacking glandular hairs on sporangial stalks and capsules; spores pale, tan, bilateral, monolete, perispore often coarsely echinate or with reticulate crests ( Tryon & Lugardon 1991; Patel et al. 2019a); x = 36, 34?, three spp. counted, C. auriculata diploid and tetraploid, C. omeiensis apparently octoploid (n = c. 136; Kurita 1966), the highest ploidy reported in Thelypteridaceae . There are at least three counts apparently based on x = 34, which, if true, is aberrant among cyclosoroid ferns (e.g., Wang & Sun 1982; Tsai & Shieh 1983).

Diagnosis.— Cyclogramma can be readily distinguished from other cyclosoroid genera by a combination of characters, including exindusiate sori, free veins, hooked hairs on the axes abaxially, as well as similar hairs on sporangial capsules. The only other paleotropical genus with hooked hairs is Grypothrix , which differs in having anastomosing veins and more shallowly incised pinnae. Cyclogramma usually has creeping rhizomes, but they are suberect or erect in C.auriculata , and that species, sister to the others, also has the longest aerophores, the greatest number of reduced proximal pinnae, and cristate spores. With Leptogramma and Stegnogramma , which are also exindusiate, Cyclogramma agrees in having creeping rhizomes, and blades often lacking reduced proximal pinnae; it differs from leptogrammoid genera in usually having pronounced, conspicuous, elongate aerophores, round sori, and in the hooked hairs on blades and sporangia.

Biogeography and ecology.— Cyclogramma comprises nine species, and these are mostly restricted to western and southern China, Bhutan, Nepal, northern India, continental southeastern Asia ( Myanmar, Vietnam); a few extend their ranges into Taiwan, southern Japan, and the Philippines (Luzon; see Holttum 1976c). The most widely distributed species is C.auriculata , with outlying populations in the Philippines and perhaps Indonesia ( Lin et al. 2013).Throughout its range, Cyclogramma occurs in moist lowland to montane forests, from 300–2800 m. Seven species are restricted to southern China, the center of diversity in the genus, and most of these are rather local; six spp. are known from Yunnan.

Taxonomic and phylogenetic studies.— Cyclogramma was recognized as a discrete natural group relatively early, by the Japanese pteridologist Tagawa (1938), who published combinations for eight species. Even before that, Ching (1936) recognized it as a natural group (his group 6) within Thelypteris subg. Phegopteris ; later, Ching (1963) followed Tagawa’s lead in treating it as a genus, while comparing it to Leptogramma . Prior to that, the species had usually been treated in a comprehensive genus Dryopteris or in an even more varied and unnatural genus Polypodium (because of lack of an indusium). Holttum (1971, 1982) adopted many of Ching’s generic concepts in Thelypteridaceae , including that for Cyclogramma . An attempt at a taxonomic middle ground was offered by Smith (1990), who recognized Cyclogramma as one of 20 subgenera in a heterogenous genus Cyclosorus s.l.

All phylogenetic studies with broad sampling ( He & Zhang 2012; Almeida et al. 2016; Fawcett et al. in press) recover Cyclogramma as sister to the clade Leptogramma + Stegnogramma , in Thelypteridoideae ( Fig. 1 ). Even before molecular studies, the affinity of Cyclogramma with leptogrammoid ferns was recognized (e.g., see Smith 1990:270). Cyclogramma likely arose and diversified in Asia, along with its closest relatives.

Figures

FIG. 1. A synoptical treeillustrating relationships among genera of Thelypteridaceae based on Fawcett et al.(in press).