Gymnomitrion sichuanicum

Description: Plants blackish brown, slightly glistening, sometimes with discolored leaf margin (but never erose) making patches paler in color (grading to greyish); forming loose to dense patches; rhizomatous base well-developed, originating as geotropic stolons from plagiotropic normally leaved branches, sometimes bearing scale-like leaves; freely rhizogenous, freely branching, giving rise to sterile and fertile branches; leafy branches varying in size, mostly erect, rarely creeping (and then producing erect intercalary branched or plagiotropic stolons), from 250 – 300 to 500 – 700 μm wide, 1000 – 2000 μm long; clavate, larger branches with cupped and ventricose leaves as if containing antheridia; larger branches dorsiventrally compressed, ribbon-vermicular. Rhizoids abundant in rhizomatous part, rare on plagiotropic branches and virtually absent in erect branches, colorless to brownish and grayish. Stem freely branched in rhizogenous part, virtually unbranched in erect shoots and sparsely producing ventral leafless stolons in creeping leafy branches; orbicular in cross section, 110 – 140 μm in diameter, outer cells larger than inner and with colorless walls that look like a hyalodermis, cells have large trigones and thickened walls, 10 – 18 μm long and 8 – 12 μm wide, inner cells with brown-rusty colored cell walls, thin-walled or at least thinner than outer, 7 – 16 μm in diameter. Leaves densely imbricate, concave to cupped, sometimes distinctly ventricose (then similar to male bracts, but no antheridia found); transversely inserted, transversely oriented, shortly decurrent on both sides, with plane to slightly to evidently recurved margin, mostly evident in lower half of the leaf, varying in shape: from transversely ellipsoidal and narrowly trapezoidal (smaller) to suborbicular and ovate (larger), leaves commonly lacerate or plicate when flattened on a slide, mostly 350 – 560 × 330 – 530 μm with larger leaves to 600 × 550 μm, divided by semicrescentic (rarely widely V-shaped) sinus descending to 1 / 15 – 1 / 9 of leaf length into two acute to obtuse (never rounded) lobes. Cell size strongly varying across leaf: near base, oblong 20 – 30 × 10 – 15 μm, thin-walled, with moderately sized concave trigones and occasionally occurring intermediate thickenings; in midleaf 10 – 15 × 7 – 12 μm, with slightly thickened to thin walls with large concave to convex trigones; in lobe apices subisodiametric, ca. 7 – 10 μm in diameter, thin-walled, with concave trigones; in leaf margin near leaf base oblong, 10 – 15 × 7 – 11 μm, thick-walled, with concave trigones; cuticle smooth throughout; trigones and cell walls always colorless, while content of the cell varies in color from colorless and greenish to brown (this determines coloration of whole plant); oil bodies in midleaf cells smooth-surfaced, homogenous, 2 – 3 per cell, relatively small, 2 – 3 μm in diameter to oblong 3 – 4 × 2 – 3 μm. Dioicous? (androecia not seen). Female plants with sequential unfertilized terminal gynoecia with 1 – 3 subfloral innovations; female bracts similar to larger leaves. Other generative features unknown (Figs 2, 3).