Nothogymnomitrion R.M.Schust.
Nothogymnomitrion R.M.Schust., J. Hattori Bot. Lab. 80: 43. 1996.
Type: Nothogymnomitrion erosum (Carrington & Pearson) R.M.Schust. (≡Cesia erosa Carrington & Pearson)
Plants often in dense, unordered, compact mats, wiry, rigid, nearly terete, vermiform, creeping, erect with crowding, plagiotropic, greenish to golden brown to red-brown. Branching common but irregular, the branches lateral-intercalary, from median sector of axil or from the ventral or sometimes dorsal end of the axil; branches of 2 types: normal and leafy, and stoloniform, the microphyllous branches issuing from lower ends of leafy axes, creeping, with rudimentary 2-ranked leaves and copious rhizoids. Stems rather thick and rigid, striolate in surface view, the cortex very weakly differentiated, in a single layer of slightly larger, firm-walled cells with ± bulging free walls; medullary cells firm-walled, clearly thickened at the angles. Rhizoids colorless, few and scattered on ventral side of normal leafy axes, abundant on stolons and from all sides of axis. Leaves stiffly suberect and weakly laterally spreading, faintly dorsally assurgent, closely and densely imbricate, the insertion subtransverse, shallowly U-shaped, the insertion lines interlocking dorsally for 2–3 or more cell rows (thus lateral merophytes clearly interlocking in a zigzag manner); leaves unistratose, strongly adaxially concave, broadly ovate-deltoid or rounded-deltoid, 270–580 µm wide × 260–500 µm long, usually as wide as long, narrowed to summit, the expanded bases closely investing the stem; apex shallowly emarginate to bidentate-bilobulate, the lobes then often barely perceptible; sinus shallow to vestigial; margins flat, the marginal cells differentiated into border of hyaline, empty, thick-walled cells in 1–2(3) rows, the marginal row mostly elongated radially, ca. 7–13 × 18–36 µm, the cells typically free distally for only 0.5 or less, with the free ends projecting as irregular, extremely thick-walled, notably irregular “knobs” or finger-like, solid projections, the thickened tip at times equaling or exceeding the length of the cell lumen, the margins thus irregularly crenulate-denticulate; intramarginal cells chlorophyllose, in ± regular vertical rows, the cells in 2–several rows at the perimeter (especially in distal sector of leaf) usually pigmented, notably thick-walled, with guttulate lumina, the remaining leaf cells often devoid of strong pigmentation, with progressively thinner walls but rounded at angles, trigones lacking or small and concave-sided to, less often, medium and straight-sided; median cells 11–19 µm wide × 13–22 µm long; basal cells usually thinner-walled, 14–17 × 16–20 µm; surface conspicuously papillose, the papillae in lower parts of leaf wart-like. Oil-bodies occupying a moderate portion of cell, pale smokey grey, hyaline, (1)2–4 per middle of lamina, obscurely coarsely papillose, the spherules not bulging beyond membrane, the oil-bodies globose to subglobose, 2.5–5 µm in diam.; oil-bodies at leaf base 4–7 per cell, at leaf margins 2–3 per cell. Underleaves lacking.
Autoecious. Androecia on leading leafy shoots or ± elongated branches, terminal but becoming intercalary, the shoots sometimes repeatedly androecial, compactly spicate; bracts leaf-like but larger, more spreading and more strongly concave (the androecia thus appearing tumid), the dorsal margin without lobule, but with dorsal margin incurved and ampliate; antheridia 2 per bract, the stalk unistratose but with local bistratose areas, particularly toward base. Gynoecia terminal on leafy axes or branches of variable length, completely lacking a subtending perigynium; bracts in several, progressively larger series (and becoming several times the size of stem leaves), closely imbricate, those of innermost series very variable, symmetrically ovate to ovate-deltoid, short-bilobed, with margins as in leaves but often even more coarsely crenulate-denticulate, the projecting thick-walled hyaline cells sometimes recurved; bracteole always present, rather large, rarely wholly free, usually connate on one or both sides with the bracts (sometimes so broadly so on one side that a 3-lobed bract is simulated). Perianth well developed, not or barely exceeding the innermost bracts, when immature ± strongly laterally compressed, at maturity the mouth remaining perceptibly laterally compressed toward the mouth, proximally inflated, ovate, with a narrowed base; mouth narrowed, shallowly bilabiate, irregularly crenulate-denticulate, with maturation soon becoming erose; perianth cells similar to leaf cells, quadrangular to short-rectangular, slightly thin-walled. Calyptra with unfertilized archegonia at or near base.
Seta very short, usually not protruding capsule beyond bracts, with 22–24 rows of outer cells surrounding an inner core of ca. 30–32 rows, the outer cells not larger than the internal cells. Capsule subspherical, the wall ca. 24 µm thick, 2-stratose, the outer ca. 2× the inner in thickness; outer layer of cells with strong, nodular thickenings that are often stalked and dilated distally, sporadically extending as weak semiannular bands, the transverse walls also with nodular thickenings; inner layer of cells with nodular thickenings, occasional ones extended as tangential spurs, a few as weak semiannular bands.
Spores brown, 10–14 µm in diam., appearing finely punctate, the spores ± equal to elater diam. Elaters 9–11 µm wide, the tips always rounded, the elaters 3-spiral throughout or at least medially and bispiral toward the ends, the spirals narrow, 1.6–2 µm wide.
A monotypic genus, with only the subantarctic Nothogymnomitrion erosum. Description adapted and modified from Schuster (1996d).
References: Grolle (1966b); Schuster (1996d, 2002a).
