Gymnomitrion blankae Mamontov, Potemkin & Vilnet, 2022

Gymnomitrion blankae Mamontov, Potemkin & Vilnet View in CoL , sp. nov., Figs. 2–5 View Fig View Fig View Fig View Fig .

Diagnosis. Cinnamon to rusty plants, with leaves somewhat turned dorsally, contiguous to loosely imbricate, bilobed for 0.34–0.47 of their length, with margins rolled backwards through the whole length, with longer ventral lobes, with apiculate lobes bearing rolled apiculi, with long bleached dorsal and ventral decurrencies; the leaf and stem surfaces smooth; the stem in transverse section with ± thinned outer walls of flattened outer cortical cells forming indistinct hyalodermis.

Type: China, Yunnan, Luquan Co., Jiaozixueshan Mtn., ca. 115 km N of Kunming, between lower and middle chair lift station, 26°05’04”N, 102°50’45”E, 3670 m a.s.l., 25.IX.2006, Blanka Shaw 5764, det. by J. Váňa as Marsupella revoluta (DUKE-180581 – holotype, LE B-0026804 – isotype).

Etymology. The species is named after its collector Dr. Blanka Aguero (when collecting Blanka Shaw ).

Description. Plants ca. 15–20 mm long × 0.7–1.5 mm wide when wet, 0.2–0.4 mm wide when dry; cinnamon to rusty when wet ( Fig. 3 View Fig : A–D), darker rusty to fuscous brown when dry ( Fig. 2 View Fig : A–F), with no traces of red pigments, with contiguous to loosely imbricate leaves. Branching rare, lateral intercalary, from upper part of the leaf axil in older shoot sectors. Rhiziods lacking or single ones. Stem rigid, in transverse section ca. 450 µm wide × 370 µm high, with 4–5-stratose cortex of 3–4 layers of yellow to brown, rounded strongly thick-walled intracortical cells, and yellowish to nearly colorless, flattened along the stem surface outer cortical cells with thinner but ± thickened walls with smooth surface forming ± distinct hyalodermis. Leaves contiguous to loosely imbricate, clearly directed to the dorsal side, oblique broadly oval to ovate, with stronger convex ventral margins, longer than wide, ca. 0.9–1.2 mm long × 0.7–0.8 mm wide, subtransversely inserted, distinctly long decurrent both dorsally and ventrally ( Fig. 5 View Fig : A–D), with bleached decurrent strips, bilobed; lobes ovate to triangular, usually apiculate with rolled apices ( Figs. 3 View Fig : I, 4: O–S), unequal with always longer ventral lobes; sinus γ- or v-like (0.27–)0.34–0.47 of the leaf length, often somewhat reflexed; undivided part of leaves convex medially, becoming plane to the margins; the margins rolled backwards throughout, i. e., from lobe apices to the decurrent strips and the base of the sinus; width of rolled backwards part from 1 to 6 cells, in distal and proximal parts of leaves narrower, 1–3 cells wide, and in median part of older leaves broader, up to 6 cells wide. Leaf areolation different in proximal and distal parts of leaves. Cells near the base longer and broader, occasionally partly extending to median part of leaves, 10–15 × 20–40 µm, thick-walled with small to larger bulging trigones, usually yellowish. Median and distal cells mostly subisodiametric, with thin wall and rectangular and quadrangular angular thickenings with convex walls, ca. 10 µm, rusty brown. Marginal cells subisodiametric, similar to marginal cells, small- er, 5–8 µm in diam. or elongated perpendicular to the margin, 8–10 × 5–7 µm, mostly thin-walled or thick-walled because of confluent angular thickenings. Leaf surface smooth. Dioicous. Androecia intercalary, slightly distinct from the sterile shoot sectors. Bracts in 2–3 pairs, similar to sterile leaves, with hardly to moderately convex bases, 2–4-androus. Antheridia on long 2-seriate stalks. Paraphyses lacking. Female plants not seen.

Distribution and Ecology. Yunnan, China. Known from the type locality only, where it was collected on vertical base-rich stone face, little shaded in open Abies- Rhododendron mixed forest on W-facing steep wet rocky slope.

Differentiation. Gymnomitrion blankae , being similar to European G. revolutum ( Figs. 6–8 View Fig View Fig View Fig ), is distinct in lighter and not characteristic of G. revolutum cinnamon to rusty color, Fig. 2 View Fig :A–D (vs. fuscous, blackish or olive fuscous, Figs. 6 View Fig : A–D, F, G, 7: A–D); leaves with sinus often γ- like and ± reflexed, Figs. 2 View Fig : G–L, 4: F–L vs. sinus usually V- or U-like not or slightly reflexed, Figs. 6 View Fig : J–M, P, Q, 7: F–H; apiculate and rolled lobe apices, Figs. 3 View Fig : I, 4: O–S (vs. rounded to blunt to shortly acute, not or slightly rolled, Figs. 6 View Fig : 0, 9: A–O); leaf surface smooth in transverse sections, Figs. 3 View Fig : J–L, 5: I–N and angular thickenings not glistening, Fig. 4 View Fig : M, N (vs. leaf surface bearing dome-shaped projections above the cell wall intersections, Figs. 6 View Fig : H, I, 8: M–O, making angular thickenings locally glistening, Fig. 6 View Fig : N); stem with ± thinned outer walls of flattened outer cortical cells forming the indistinct hyalodermis, Fig. 3 View Fig : G, H (vs. with thickened outer walls of often not flattened outer cortical cells, not forming hyalodermis, Fig. 6 View Fig : E); base-rich (vs. acidic) habitat; the Sino-Himalayan vs. European distribution.

Noteworthy that leaves of Gymnomitrion blankae often have coarser trigones ( Fig. 4 View Fig : M) and smooth surface whereas leaves of G. revolutum in general have smaller trigones ( Fig. 6 View Fig : N) and papillose surface. Moreover, leaves of dry shoots of G. blankae are usually distinctly turned to the dorsal side of stem, whereas leaves of dry shoots of G. revolutum are less often turned to the dorsal side of the stem.