Oreogrammitis parvula Parris, 2015

Oreogrammitis parvula Parris View in CoL sp. nov. ( Figure 2 View FIGURE 2 )

Oreogrammitis parvula differs from other members of the genus in its combination of the following characters: narrowly oblanceolate laminae less than 30 mm long, veins simple or with a very short acroscopic branch bearing the sorus, and lamina hairs 1–3 mm long.

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!).