Terrestrial ferns of moderate to large size, sometimes small. Rhizome an erect or ascending, less often long-creeping, radially symmetric caudex, dictyostelic, almost always bearing narrow scales with many superficial and marginal acicular hairs. Fronds long-stipitate, the stipe with 2 vascular bundles at the base uniting upward into a single U-shaped vascular strand, lamina pinnate with crenate to deeply pinnately lobed pinnae, in almost all species several pairs of basal pinnae gradually reduced and almost always auricled on the acroscopic side, aerophores at bases of pinnae not swollen, margins entire, midribs of pinnae grooved above, but the grooves not confluentwith rachis groove, erect, unicellular, acicular hairs and abundant on abaxial surface, mostly alsoon adaxial surface, short capitate hairs often present, thick orange-red glandular hairs sometimes present below, sessile spherical glands lcaking, veins in a pinnate group in each pinna-lobe or crenation, mostly at least the basal pair of each group anastomosing to form an excurrent vein terminating in the sinus membrane, the remaining veinlets simple, free, terminating in the magin above the sinus membrane, in a few deeply lobed species all veins free. Sori round, indusiate, rarely exindusiate, medial or distal on the veins; sporangi on a 2-seriate stalk bearing an elongate unicellular glandular hair for an acicular hair) or not, the annulus longitudinal interrupted. Spores monolete, dark, nearly black, variously tuberculate or ridged, without thin wings.
Sect. Christella: plants of normal size, not restricted to limestone; veins nearly always anastomosing, at least the basal pair to form an excurrent vein terminating in the sinus membrane, rarely all veins free; hairs on sporangia stalks elongate-glandular. (Paleotropics).
Sect. Leptochristella: reduced plants (pinnae mostly less than 4 cm long of limestome; veins free or infrequently anastomosing; hairs on sporangium stalks, if present, acicular. (Papuasia).
Sect. Pelazoneuron: plants of normal size, not restricted to limestone; veins always free, the basal acroscopic vein terminating the sinus membrane, the basiscopic vein of the next group terminating above the sinus, rarely the two casually anastomosing in some pinnae to form an excurrent vein; hairs on sporangia stalks acicular. (Africa and Neotropics).
Key modified ex Holttum 1981, F1. Males. ser. 2, 1:553 and 1977, Allertonia 1:216.
Species in Papuasia
|1a.||Reduced plants of limestone; pinnae not over 4.5 cm long; no elongate hairs on stalks of sporangia||(sect. Leptochristella)
|Plants of normal size, not confined to limestone; pinnae commonly 10 cm or more long; elongate glands present on stalks of sporangia||(sect. Christella)
|2a.||Indusia distinctly present||3|
|Indusia lacking or not clearly distinguishable||C. nana|
|3a.||Pinnae to 27 pairs, 5-7 lower ones gradually reduced||C. perpubescens|
|Pinnae c. 6 pairs, the lowest only slightly reduced||C. minima|
|4a.||Veins all free (sometimes basal pair casually anastomising)||5|
|At least the basal veins regularly anastomosing||7|
|5a.||Red ellipsoid glands lacking||C. peekelii|
|Red ellipsoid glands present on lower surface of pinnae||(C. harveyi)
|6a.||Pinnae lobed to 1.5 mm form costa; basal veins free to sides of sinus membrane; 2-4 pairs of basal pinnae gradually descrescent||C. harveyi var. harveyi|
|Pinnae less deeply lobed; basal veins occasionally uniting below sinus membrane; c. 10 pairs of basal pinnae gradually decrescent||C. harveyi var. connivens|
|7a.||At least 3 pairs of basal pinnae gradually reduced||8|
|At most 3 pairs of basal pinnae gradually reduced||12|
|8a.||Sinus membrane prominent on lower surface, 3 pairs of veins ending beside it; reduced pinnae hardly auricled||C. arida|
|Sinus membrane not prominent, at most 1.5 pairs of veins ending beside it; reduced pinnae clearly auricled||9|
|9a.||Caudex strictly erect||10|
|Caudex short-creeping or at most suberect distally||11|
|10a.||Pinna lobed less than 1/2 way to costa; hairs on lower surface of costae all less than 0.5 mm long||C. adenopelta|
|Pinnae lobed more than 1/2 way to costa; hairs on lower surface of costae mostly more than 0.5 mm long||C. hispidula|
|11a.||Pinnae lobed at least 1/2 way to costa; only one pair of veins truly anastomosing; some hairs 0.3 mm long present on lower surface of costae.||C. dentata|
|Pinnae lobed 1/4-1/3 towards costa; at least 1.5 pairs of veins truly anastomosing; all hairs on lower surface of costae c. 0.1m long||C. subpubescens|
|12a.||Hairs on lower surface of costae all very short||C. subpubescens|
|Hairs on lower surface of costae always conspicuous, to 1 mm long||13|
|13a.||Caudex long-creeping||C. parasitica|
|Caudex short-creeping or erect||14|
|14a.||Pinnae lobed much more than 1/3; some hairs more than 0.5 mm long present on the lower surface||15|
|Pinnae lobed little more than 1/2; hairs on lower surface all less than 0.5 mm long||C. dentata|
|15a.||Caudex erect; 2 or more pairs of lower pinnae reduced||C. hispidula|
|Caudex not erect; basal pinnae not reduced.||C. parasitica|