Haplopteris angustissima (Holttum) S.Linds., Gard. Bull.

Haplopteris angustissima (Holttum) S.Linds., Gard. Bull. View in CoL Singapore 62: 119. 2010. Vittaria angustissima Holttum, Gard. Bull. View in CoL Singapore 11: 274. 1947. TYPE: MALAYSIA. Pahang: Fraser’ s Hill,

1219 m [4000 ft], Mar 1929, C.E. Carr s.n. (holotype: SING! [SING0144295]).

Epiphytic or lithophytic. Rhizome short-creeping, densely scaly, ca. 1 mm diam including scales, bearing fronds close together. Rhizome scales narrowly lanceolate, gradually narrowing from the base towards a long-tailed and ultimately filiform apex, 0.8–1.8 mm long and 0.2–0.3 mm wide (at base), clathrate, toothed at margin, the walls thickened and dentate. Fronds sessile, simple, linear, 2.0– 13.2 cm long, 0.5–0.8 mm wide, widest above the middle, gradually narrowing towards both ends, apex acute or (occasionally) truncate, laminae coriaceous, glabrous, margins entire, flat on both surfaces. Venation difficult to see even with transmitted light, in fronds with single sori, midvein branching near frond base into two very close parallel main veins and reuniting near the frond apex, a few oblique lateral veins between the two main veins, forming a few long, narrow areoles; in fronds with double sori (our observation is based on the examination of one frond), midvein branching into three almost parallel main veins (midvein and two lateral veins) near frond base, very sparse oblique lateral veins present only on one side of midvein. Epidermal silica bodies linear, 0.1–0.7 mm long, present on both sides of the lamina, margin lobed, ends of lobes pointed. Sori linear, uninterrupted, following one main vein, slightly covered by a soral flap and open to one side, or rarely, fertile on both sides, each following a lateral main vein. Soral paraphyses copious, stalks uniseriate, filiform, colourless; apical cells large, funnel-shaped, length-to-width ratio of 1.1 6 0.23, yellowish. Spores bilateral, bean-shaped, monolete, yellowish, surface smooth.

Distribution —Peninsular Malaysia. Known from only three areas on the Main Range (Fraser’ s Hill, Gunung Kerbau, and Cameron Highlands).

Ecology —Epiphytic on mossy tree trunks in damp forests or lithophytic on quartz outcrops near the ridge of mossy forests. The lowest recorded elevation is 1200 m and the highest is 1730 m.

Additional Specimens Examined —Malaysia. — PENINSULAR MALAYSIA: Pahang, Cameron Highlands, 1524 m [5000 ft], 4 Mar 1948, Molesworth

Allen , B.E.G. 1061 (K![K000637847]); Pahang, Cameron Highlands, slope of G. Jasar, 1615 m [5300 ft], 20 Apr 1958, Molesworh Allen , B.E.G. 3928 (K! [K000637844]); Pahang, Cameron Highlands, [See note below concerning discrepancies in locality data], underside of sloping trunk hanging over stream in tall dark forest.A mossy place.Only one patch (but found in other localities), rare, 1524 m [5000 ft], 22 Apr 1958, Molesworth Allen , B.E.G. 3941 (K!, SING! [SING0085700]); Pahang, Cameron Highlands, Many fronds now dead, others medium green. In small clumps, very dwarfed, looking like Monogramma trichoidea . Abundant locally on vertical sites, in tiny crevices on the actual rock. Quartz outcrop [sometimes called “Castle Rock”] beyond Brinchang Village., 1615 m [5300 ft], 9 Feb 1959, Molesworth Allen , B.E.G. 4135 (K!, 2 sheets [one with barcode K000637843], the other without barcode, US! [ US 01483064]); Pahang, Cameron Highlands, Brinchang Village, trail to Coral hill, lithophyte on quartz outcrop, rare, 4.495282°, 101.3955°, 1730 m, 5 Jul 2017, Chen, C.-W. Wade4825 (KLU!), TAIF! [TAIF513482]); Pahang, Cameron Highlands, on Jacob’ s ladder, on underside of root base tangle, in very damp and dark position, 1524 m [5000 ft], 25 Oct 1965, Evans 118 (KLU!); Pahang, Fraser’ s Hill [“Bukit Fraser”], 1219 m [4000 ft], Jun 1922, Smith , E. 899 (K! [K000637846], SING! [SING0085650]); Pahang, Frasers Hill, upon the Selangor border, epiphyte on tree stump among moss. 1219–1331 m [4000–4370 ft], 26 Sep 1922, Burkill, I.H, & Holttum, R.E. 8835 (SING! [SING0085634, SING0085635]); Pahang, Fraser’ s Hill, 1280 m [4200 ft], 20 Apr 1957, Molesworth Allen , B.E.G. 3347 ( US! [ US 1485955]); Perak, Gunung Inas, 1158 m, 7 Dec 1899, Yapp, R.H. 417 (K! [K000637845]); Perak, Gunong Kerbau, 1371 m [4500 ft], May 1909, Haniff, M. 3938 (SING! [SING0085673]).

Notes —1) The two sheets of Molesworth Allen 3941, from the Cameron Highlands show the same elevation data, collection date, and ecological information, but the one at K is labelled “slopes of G. Kemmiting” whereas the one at SING is labelled

“Forest above Walkerburn Cottage.” 2) The locality of Chen Wade4825 is possibly the same locality as Molesworth Allen 4135.