Gymnomitrion vietnamicum Bakalin et Vilnet, 2023

Bakalin, Vadim, Vilnet, Anna, Klimova, Ksenia, Nguyen, Van Sinh & Choi, Seung Se, 2023, Gymnomitrion vietnamicum (Gymnomitriaceae, Marchantiophyta) - a new species from North Indochina, Phytotaxa 616 (1), pp. 47-59 : 52-53

Gymnomitrion vietnamicum Bakalin et Vilnet sp. nov.

Description: Plants rusty brown to blackish and deep blackish green, without purple pigmentation, rigid, erect to distinctly ascending, 2.0– 2.7 mm wide and 20–45 mm long, forming loose pure patches. Rhizoids virtually absent in leaved shoots, but common in ventral leafless stolons, in spreading loose fascicles or separated, colorless to brownish and purplish. Stem rigid, blackish, freely branched, branches of two types: 1) intercalary from the postical side of the leaf sinus, becoming normally developed shoots, 2) ventral leafless stolons, sometimes branched multiple times; cross section transversely elliptic, 220–250 × 250–280 µm with pronounced cortex, gradually turning to medullar tissue inward, outer cells 7–10 µm in diameter, very thick-walled, with lumen only 2–4 µm in diameter, distinct red-rusty middle lamina, cortex in 3–4 rows of cells, inward cells becoming larger and thinner-walled, though walls are never thin, 15–24 µm in diameter, moderate in size, concave trigones, no visible middle lamina. Leaves closely sheathing stem, contiguous, distinctly ventrad (turned ventrally), transversely inserted, shortly decurrent on both sides of stem, with distinctly and narrowly recurved margin, on slide (when pressed by cover slip) 1.2–1.5 × 0.9–1.1 mm, divided by gamma-shaped sinus descending to 1/3–2/5 of the leaf length into two slightly gibbous and acute lobes with their midlines turned ventrally (lobes therefore slightly falcate), lobes subequal, with ventral lobe slightly smaller, terminated by narrow triangular end 5–6 cells long for 3–4 cells wide in the base. Midleaf cells above vitta bifurcation oblong, 15–25 × 12–15 µm, with large, nodulose, commonly confluent trigones, sometimes vermiculate in longer walls, vitta indistinct, in lower 1/4 of the leaf length, with cells 25–60 × 7–11 µm, with vermiculately thickened walls, above lower 1/4 gradually becoming normal cells as described above, with two unclear, divaricate rows going in the direction of lobe midlines, but actually never reaching lobes; cells in lobe middle oblong, 13–20 × 8–13 µm, with walls slightly thickened and large, nodulose and commonly confluent trigones that make space between trigones hardly observable; middle lamina well observable through the leaf except of vitta cells in the leaf lower part; cuticle smooth throughout, except verruculose in narrow apices of leaf lobes.?Dioicous (androecia not seen). Female bracts similar to leaves, perigynium absent or very low, gynoecia surrounded by 3 pairs of bracts, tightly enclosed one to another, perianth absent. Seta 2.0– 3.5 mm long (including the part ‘hidden’ in the perichaetium), capsule spherical, 1.2–1.4 mm in diameter; capsule wall bistratose, inner cells rectangular, 25–50 × 10–20 µm with nodular thickenings in each vertical wall and the majority of horizontal walls, outer cells shortly rectangular to oblong, 25–30 × 20–25 µm, with 1–6 nodular thickenings in almost each vertical wall (some vertical walls are thickenings free) and 0–2 in each horizontal wall. Spores papillose, spherical, brown, 13–15 µm in diameter. Elaters bispiral, 200–230 × 5–6 µm, with narrow, but not homogenous ends (thus the walls at the end of the elaters are not confluent and inner content remain visible). ( Figs 2 , 3 )

Holotype:— VIETNAM. Lai Châu Province: Ta Leng Commune, Pu Ta Leng Range, evergreen south subtropical mountain forest in stream valley. Open moist boulder near stream, 2202 m a.s.l., 22.41972°N 103.59083°E, 27 March 2018, V. A. Bakalin & K. G. Klimova V-6-10-18 ( VBGI, isotype in KPABG).

Paratype:—Same locality (part of the holotype, but collected in a separate envelope), 27 March 2018, V. A. Bakalin & K.G. Klimova V-6-15-18 (VBGI).

Figures

FIGURE 2. Gymnomitrion vietnamicum Bakalin et Vilnet: A—plant habit, ventral view; B—plant habit, dorsal view; C—habit of sporogenous plant, lateral view; D–J—leaves (D–F—adaxial, G–J—abaxial views); K—fragment of stem cross-section. Scales: a—1 mm, for A–C; b—1 mm for D–J; c—100 µm for K. All from V-6-10-18 (VBGI). (Line drawings by M. Bakalin, 2022).

FIGURE 3. Gymnomitrion vietnamicum Bakalin et Vilnet: A—cells in the leaf apex; B—part of mat; C—spores and elaters; D— sporogenous shoots in the mat; E—cells near rolled leaf margin; F—midleaf cells; G—midleaf cells above vitta bifurcation. Scales: 50 µm, for A, C, E–G; 5 mm for B, D. A, B, E from V-6-10-18; C, D, F, G from V-6-15-18 (VBGI). (Photo by V. Bakalin, 2018)