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Belchnum L.

Erect, or rarely rosette, terrestrial ferns of small to moderate and large size. Rhizome stout, erect or ascending, sometimes subarborescent, sometimes creeping or scandent, bearing clustered fronds, radially symmetric, dictyostelic, densely covered with dark, glossy, often harsh, basally attached scales. Fronds mostly long-stipitate, the stipe with several vascular strands arranged in a ring, naked or with reduced auriculate pinnae, not articulate to the rhizome, the lamine +/- lanceolate, deeply pinnatifid or pinnate, rarely simply, sometimes bipinnatifid, the pinnae shortly stalked, sessile or broadly adnate, firm usually glabrous, sometimes finely harily, margins entire or serrulate, cartilaginnous; veins free (except in the sorus), forked, terminating in the cartilaginous marginal strand; the lamina of fertile fronds sometimes strongly contracted. Sporangis borne in a continuous elongate coenosorus on a continuous fertile vein or commisure adjacent and parallet to the costa, protected by a continuous introrse indusium attached to the marginal side of the commisure, the non-soriferous part of the lamina normal or reduced to a narrow band hardly extending beyond the indusium; paraphyses lacking, annulus longitudinal, interrupted, of 14 - 28 thickened cells. Spores monolete usually smooth, sometimes with a perispore, papillose to variously folded.

Subg. Blechnum: Sterile lamina in fertile pinnae not contracted, similar to sterile pinnae.

Subgen. Lomaria: Sterile lamina in fertile pinnae reduced to a narrow wing hardly extending beyond the indusium.

Species in Papuasia

1a. Fronds alike, sori not covering lower surface...
2
Fronds dimorphic, fertile fronds with contracted linear pinnae or lobes +/- entirely covered by sporangia...
5
2a. Margin entire...
3
Margin serrate...
4
3a. Rachis blackish beneath; pinnae (1.5 - ) 2 - 3 cm wide, c. 10 - 2- pairs, the apical lobe not much reduced; plants of shade...
B. finlaysonianum
Rachis stramineus; pinnae c. 1 cm wide, to 40 pairs or more in mature plants, the apaical lobe much smaller than the lateral lobes; plants of open situations...
B. orientale
4a. Pinnae c. 6 pairs, the apical pinna +/- free and of similar size to the lateral pinnae; scales at base of stipe linear, c. 12 mm long, black...
B. nigropalaceum
Pinnae to 20 or more pairs, reduced apically, the terminal pinna much smaller than the laterals; scales at base of stipe lanceolate, 1 - 2 mm long, brown...
B. serrulatum
5a. Fronds bipinnatifid or subbipinnate or with deeply serrate dsterile pinnae; minature tree ferns...
6
Fronds pinnate or pinnatifid, with at best find serrations, rarely arborescent...
7
6a. Fronds deeply bipinnatifid, the lobes entire, a fiarly abrupt transition between the basal pinnae and the reduced pinnae along the stipe...
B. fraseri
Fronds pinnante, the sterile pinnae deeply serrate, the basal pinnae gradually and +/- evenly reduced towards the base of the stipe...
B. rosenstockii
7a. Nearly all sterile pinnae confluent or adnate...
8
Most pinnae free...
13
8a. Lowermost pinnae free and not adnate...
9
All sterile pinnae confluent or adnate...
11
9a. Lamina glabrous beneath; scales at base of stipe black...
B. dentatum
Lamina with fine hairs beneath; scales at base of stipe brown...
10
10a. Pinnae c. 20 - 3- pairs; caudex stout and erect, aborescent...
B. vittatum
Pinnae c. 10 - 12 pairs; caudex not tree-like...
B. vulcanicum
11a. Dwarf basal pinnae remote; costae pale (?)...
12
Dwarf basal pinnae contiguous, wide; costae dark...
B. keysseri
12a. Sterile pinnae over 10 cm long...
B. saxatile

B. ledermannii

12b. Sterile pinnae up to 8 cm long...
B. borneense
13a. Dwarf basal pinnae present...
B. papuanum

Dwarf basal pinnae absent...
14
14a. Pinnae obtuse or rounded, linear or oblong...
15
Pinnae subacaute to acuminate...
16
15a. Pinnae obtuse, linear, strongly revolute...
B. revolutum
Pinae rounded, oblong, +/- flat...
B. fluviatile
16a. Pinnae entire, unless near the appex...
17
Pinnae margins not entire...
20
17a. Pinnae rounded at the base...
18
Pinnae cordate at the base...
19
18a. Pinnae c. 12 cm long...
B. pendulum
Pinnae c. 6 cm long; rhizome scandent...
B. brassii
19a. Apical leaflet like the others...
B. decorum
Apical pinnae confluent...
B. archoboldii
20a. Pinnae cordate...
B. decorum var. dilatatum
Pinnae rounded or tuneate at base...
21
21a. Pinnae cuneate to rounded, glabrous beneath, c. 15 - 3- cm long...
B. procerum
Pinnae rounded to truncate or subcordate, scaly along costae, c. 7 -15 cm long...
22
21a.? Costae densely scaly...
B. hieronymii
21b.? Costae sparingly squamulose...
B. acutiusculum