Tên Khoa học: Oreogrammitis parvula Parris
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Type:—Vietnam. Khanh hoa Province: hon Ba Nature reserve, elev. 1500 m, 26 January 2014, Wade 3725 (holotype TaIF!; isotype aK!).

Rhizomes dorsiventral, stipes in two rows, not articulated to rhizome; rhizome scales 1.4–1.7 × 0.2–0.3 mm, medium yellow-brown, glabrous, not clathrate; stipes 4–6 × 0.1–0.2 mm; laminae 15–23 × 2–3 mm, narrowly oblanceolate, obtuse to bluntly acute at apex, long-attenuate at base, entire; midrib sometimes slightly prominent and concolorous to slightly darker on abaxial surface, not evident on adaxial surface; sterile veins simple, fertile veins simple or 1-forked, acroscopic branch very short, not extending beyond sori; sori ± circular to broadly elliptic, in apical 1/6 to 1/3 of lamina, one row each side of midrib, 1–7 in each row; sporangia with 1–2 setae at apex; medium to dark red-brown setae dense on stipe (0.9–1.1 mm long), occasional to scattered on lamina (1.2–3.0 mm long), longer on adaxial surface of lamina and midrib than on abaxial surface of lamina and midrib, and on margin.

Distribution and habitat:—endemic to Vietnam, only known from hon Ba Nature reserve.

Etymology:—Latin, parvula = diminutive of parva (= small), very small, referring to the size of the fronds.

Taxonomic note:—This species could be confused with Radiogrammitis beddomeana (alderw.) Parris, another dwarf simple-fronded grammitid, which differs in radial rhizomes without scales and whitish to pale red-brown setae.

Additional specimens examined:—Vietnam. Khanh hoa Province: hon Ba Nature reserve, elev. 1454 m, 29 December 2011, Luu Hong Truong & Tran Gioi KH 0057 (SgN!).

(Phytotaxa 226 (1): 039–050)