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Adiantum L.

Erect ground fern or climbing epiphyte starting from the ground, of small to moderate size. Rhizome long-creeping and solenostelic, or compact, ascending and dictyostelic, the young parts clothed in narrow, dark, sometimes pale-margined, entire or toothed, basally attached scales. Fronds long-stipitate, the stipes +/- terete, dark and polished, scaly at the base, with 2 ribbon-like, +/- parallel vascular strands uniting upwards, to form a single 4-angled strand, the lamina simple, pinnate or up to 4-pinnately decompound, usually broad, the axes dark and polished, pinnules dimidiate or cuneate-flabellate, the margins entire, or toothed or notched, texture membranous to coriaceous, usually herbaceous, glabrous or variously hairy, sometimes glaucous, the veins usually free, flabellate, dichotomously branched from the base, sometimes irregularly anastomsing. Sporangia in sori borne on veins on the under surface of reflexed marginal lobes, the veins simple and parallel, continuous into the lobes, the lobes a pseudoindusium completely protecting the sorus, reinform at the base of a notch, orbicular or elongate-oblong on a tooth or entire margin, or elongate and uninterrupted along the side of the pinnule, paraphyses lacking, sporangia on long, 3-seriate stalks, annulus longitudinal, interrupted, of c.18 thickened cells. Spores trilete, sometimes monolete, dark, smooth.

Sect. Reniformiae: fronds simple.

Sect. Oligisoriae: fronds pinnately divided; leaflets not cuneate-flabellate; sori linear, in continuous or interrupted lines.

Sect. Polysoriae: fronds pinnately divided; leaflets not cuneate-flabellate; sori transeverse-oblong, or reniform

Sect. Cuneatae: fronds pinnately divided; leaflets cuneate-flabellate; sori reniform, sometimes transverse oblong.

Sect. Pedatae: fronds +/- pedate-dichotomous (forked with the secondary branches arising from the upper side of the 2 primary ones); sori reniform.

Sect. Hewardia: veins anastomosing.

Species in Papuasia

1a. Fronds simply pinnate, often proliferous at their apex...
2
Fronds more compound, or if simple then not proliferous at the apex...
3
2a. Frond glabrous; pinnae semicircular, subcuneate, on stalks to 10 mm long; rachis naked...
A. philippense
Frond with pale red hairs; pinnae dimidiate, oblong, on short stalks less than 1 mm long; rachis hairy above...
A. caudatum
3a. Fronds with pale or red hairs beneath...
4
Fronds naked (except adaxial side of rachis)...
5
4a. Fronds filmy, with dark red hairs beneath...
A. diaphanum
Fronds firm, with stiff pale hairs beneath...
A. hispidulum
5a. Stipe at most 10 cm long...
A. kingii
Stipe at least 15 cm long...
6
6a. Pinnules cuneate-flabellate, c.1 cm across, or large (2 x 4cm) and trapezoid...
7
Pinnules dimidiate, if trapezoid then less than 1 cm wide...
10
7a. Large plants with acute trapezoid pinnules c.2 x 4cm, on stalks c.1 cm long; sori +/- oblong, along the acroscopic and outer margins...
A. trapeziforme
Small to medium plants with rounded cuneate-flabellate pinnules on much shorter stalks; sori shorter and along the distal margin...
8
8a. Pinnules conspicuously articulate to their stalks which are swollen at the apex; sori short, straight, along the apices of lobes...
A. tenerum
Pinnules confluent with their skills; sori orbicular-reniform with deep sinuses...
9
9a. Pinnules with the outer edge shallowly lobed...
A. aethiopicum
Sterile pinnules conspicuously toothed...
A. cuneatum
10a. Sori orbicular, climbing epiphytes...
A. neoguineense
Sori wider than long, terrestrial...
7
11a. Rachis hairy above; sori narrow...
A. christii
Rachis glabrous; sori wide, 1-3 per pinnule...
A. hollandiae

****Insert Adiantum monosorum from the Solmons ****