Sect. Cyathea
Indusium at first covering sorus, apical part very thin and caducous, an irregular almost flat disc remaining on old sorus
. . . . . . . . . . C. acanthophora
Indusium otherwise or lacking
Indusium covering sorus to maturity, then breaking and persistent
Pinnules to 2.5 cm. long, less than 10 mm. wide
. . . . . . . . . . C. havilandii
Pinnules to at least 45 x 10 mm, in most cases much larger
Largest pinnules more than 100 x 20 mm; costules 5 mm. or more apart
. . . . . . . . . . C. longipes
Largest pinnules not over 100 x 20 mm; costules 3-4.5 mm. apart
. . . . . . . . . . C. oosora
Indusium hemitelioid (sometimes almost covering sorus to maturity, sometimes very small) or lacking
Indusium entirely brown and rather firm, quite covering sorus to maturity, breaking only when old
. . . . . . . . . . C. loheri
Indusium in part pale and fragile, breaking at maturity, or not entirely covering sorus
Indusium visible as a scale backing the costule, not entirely hidden by sorus
. . . . . . . . . . C. borneensis
Indusium very small, hidden by sporangia
Pinnules commonly more than 20 mm. wide
. . . . . . . . . . C. incisoserrata
Pinnules commonly under 20 mm. wide
Paraphyses conspicuous, longer than sporangia, 2-3 cells wide at base
. . . . . . . . . . C. latebrosa
Paraphyses shorter than sporangia, slender
Pinna-rachis hairy towards apex on lower surface; lower pinnae much reduced and spaced
. . . . . . . . . . C. borneensis
Pinna-rachis not hairy on lower surface; lower pinnae not greatly reduced
. . . . . . . . . . C. acanthophora
Sect. Gymnosphaera
Reduced pinnae present at base of stipe, separated from normal pinnae
Segments of reduced basal pinnae all with very narrow lamina, forming a wing along each side of the veins
. . . . . . . . . . C. ramispina
Segments of reduced basal pinnae all with broad lamina
. . . . . . . . . . C. recommutata
Reduced pinnae, separate from the rest, lacking; lower pinnae in some cases reduced gradually almost to base of stipe
. . . . . . . . . . C. glabra
Subsect. Sphaeropteris
. . . . . . . . . . C. leucotricha
Subsect. Fourniera
. . . . . . . . . . C. tripinnata
Subsect. Schizocaena
Fronds simply pinnate, pinnae entire or at most serrate-crenate
Apex of frond a deltoid deeply lobed lamina; pinnae sessile, base truncate or subcordate
. . . . . . . . . . C. capitata
Apex of frond a pinna of same shape as other pinnae; pinnae usually stalked
Pinnae not over 15 mm. wide, base narrowly cuneate, stalks to 12 mm. long; sori in 1-2 rows on each side of costa, fully indusiate
. . . . . . . . . . C. angustipinna
Pinnae 2-4 cm. wide, base rather broadly cuneate, stalked or not; sori in fully fertile fronds in more than 2 rows, indusiate or not
Pinnae not long-acuminate, upper usually sessile
. . . . . . . . . . C. moluccana
Pinnae long-acuminate, all stalked
. . . . . . . . . . C. arthropoda
Fronds simply pinnate with deeply lobed pinnae, or bipinnate
Fronds simply pinnate with deeply lobed pinnae, the largest sometimes with free pinnules at their base
Pinnae commonly 25 cm. long; no long pale hairs on rachis
. . . . . . . . . . C. alternans
Pinnae much shorter; main rachis bearing long pale hairs
. . . . . . . . . . C. elliptica
Fronds amply bipinnate
Pinnules entire or with crenate edges
. . . . . . . . . . C. alternans
Pinnules distinctly lobed
Sori indusiate
Pinnules of larger pinnae not lobed more than ¾ way to costa throughout, no free basal pinnules or sometimes one on lowest pinnule of lower pinnae
Basal pinnules of middle pinnae with stalks to at least 4 mm. long; pinnules lobed less than ½ way to costa
. . . . . . . . . . C. stipitipinnula
Basal pinnules sessile or nearly so; pinnules lobed more than ½ way to costa
Indusium a disc hidden by sorus
. . . . . . . . . . C. discophora
Indusium complete, breaking and persistent at maturity
. . . . . . . . . . C. megalosora
Pinnules of larger pinnae always with one or more free basal segments
Copious long hairs on lower surface of veins as well as costules
. . . . . . . . . . C. megalosora
No hairs on lower surface of veins
. . . . . . . . . . C. assimilis
Sori without indusia
Long-spreading hairs abundant on lower surface of rachis and/or pinna-rachis, often also on costae
Costules and veins bearing hairs on lower surface like those of costae
Pinnules to 110 mm. long, cut to ¾ to costa; costules 5 mm. apart
. . . . . . . . . . C. trichodesma
Pinnules to 65 mm. long, cut to within 1 mm. of costa; costules 3-3.5 mm. apart
. . . . . . . . . . C. wallacei
Costules and veins lacking hairs on lower surface
Hairs of lower surface confined, or almost confined, to main rachis
. . . . . . . . . . C. elliptica
Hairs of lower surface present on pinna-rachis and costae, few or none on main rachis
. . . . . . . . . . C. trichophora
Long-spreading hairs lacking on lower surface of rachis and pinna-rachis
Largest pinnules with a free segment at the base; pinnules on stalks to 4 mm. or more long; texture firm
. . . . . . . . . . C. polypoda
Largest pinnules lacking a free segment at the base, almost sessile
Bullate scales lacking on costae and costules; pinnules cut to less than 1 mm. from costa; stout erect hairs abundant on upper surface of costules and veins
. . . . . . . . . . C. agatheti
Bullate scales present on costae and costules; pinnules less deeply lobed; hairs on upper surface of costules few
. . . . . . . . . . C. squamulata
