Radula australiana K. Yamada

Forming pure turfs or mats of shoots, dark brown in herbarium; shoot systems regularly pinnately branched, with additional pseudodichotomous branching in female plants due to production of pairs of subfloral innovations below gynoecia; dimorphic, primary shoots 1.5–1.8 mm wide and up to 40 mm long, secondary shoots smaller in stature than parent shoot, 0.8–1.0 mm wide, and either apparently terminating growth after 4 to 7 leaf pairs, or producing reproductive structures and, in female plants, continuing vegetative growth; older shoot sectors retaining leaf-lobes. Stems 120–160 µm diameter, with cortical cells in a single tier of 23–29 rows, cortical cell walls yellow-brown pigmented, external free cortical cell wall continuously thickened, radial longitudinal cortical walls thin or slightly thickened, inner tangential walls thickened; medulla cells in 23–45 rows, medulla cell walls faintly yellow-pigmented, thin walled, small triangular trigones, medial walls unthickened. Cortical cells on dorsal stem surface arranged in straight longitudinal rows on young and mature shoot sectors. Leaf insertion reaching dorsal stem mid-line, leaving no dorsal cortical cell rows leaf-free; leaf insertion not attaining the ventral stem mid-line, leaving two ventral cortical cell rows leaf-free. Leaf lobes rotund, 475–920 µm long by 400–780 μm wide, contiguous, not falcate, acroscopic base not sharply deflexed away from stem, weakly concave, not or weakly interlocking over the dorsal stem surface, stem visible between leaf lobes in dorsal view; margins entire or crenulated, not repand, the interior lobe margin shallowly ampliate, reaching the opposite stem margin, antical and exterior margins more or less continuously curved, postical margin shallowly curved or straight; angle between postical lobe margin and keel 140–180°. Lobules quadrate on leading shoots, one sixth to one quarter the lobe area, 330-605 µm long by 370–595 μm wide; keel straight to shallowly curved, angle between keel and stem 100–135°, keel turning through up to 30°, keel apex and postical lobe margin flush; interior lobule margin free for one quarter to one third its length, free portion ampliate, extending half way across the ventral stem surface or more; acroscopic margin S-shaped to straight, apical portion slightly inclined toward stem or perpendicular to it; apex obtuse but usually weakly apiculate; free exterior margin straight, margins plane, entire; lobe-lobule junction level with or slightly postical to the acroscopic end of stem insertion; attached to stem along 0.66–0.75 of the interior margin, stem insertion gently curved, not revolute; lobule apex bearing a single papilla, another two papilla situated on the interior lobule margin above the stem insertion. Leaf lobe cells rounded-oblong, not arranged in rows, unequally sized, 13–35 µm long by 11–21 μm wide, thin-walled with small triangular trigones, medial wall thickenings absent; cells of lobe margin smaller than those of leaf middle, quadrate to rectangular, 11–18 µm long by 9–13 µm wide, interior walls moderately and continuously thickened, exterior wall moderately and differentially thickened at mid-wall, forming a conspicuous bulge and imparting a crenulate appearance to lobe margin; leaf lobe cell surface unornamented, smooth. Oil-bodies 2 or 3, light brown, granular, internally homogeneous, filling the cell lumen. Asexual reproduction absent. Dioicous. Androecia on branches that usually terminate after production of 4 or 5 pairs of antheridial bracts, but rarely branches indeterminate, bearing ∞ pairs of antheridial bracts; lobules epistatic, keel deeply curved, bucket-like, free apical portion triangular, apex acute, interior margin ampliate, covering ventral stem surface, and imbricate with adjacent antheridial lobules; lobes rounded, not caducous, antheridia not seen. Gynoecia terminal on branch shoots, subtended by two or three subfloral innovations that are full-sized and again fertile; archegonia 125–150 µm tall, archegonia neck five cell columns, 10 per gynoecium on a small disc of tissue, encompassed by a low protoperianth; female bracts in one pair, symmetrical, tightly imbricate, elliptic-obovate, weakly falcate, lobe 690–770 μm long by 430–535 μm wide, margins crenulate; lobules rectangular, one half to two thirds the lobe area, apex obtuse, keel straight to arched, margins crenulate; bract insertion lines interlocking dorsally and ventrally, insertion equitant. Perianths 4200–4700 µm long and 1050–1200 µm wide at mouth, mouth entire to irregular, parallel sided for upper two thirds, widening to flask shaped, faint bulb in basal third, broadest in middle of this bulb, 1200–1350 µm wide, then tapering to base. Perianth walls unistratose above, with bistratose bands extending up to half way up perianth, increasing in width toward base, becoming confluent, basal perianth walls progressively increasing in thickness, 2–3-stratose. Long stem perigynium present, 5-6 stratose, cell walls heavily thickened and brown-pigmented. Calyptral perigynium present, base of calyptra 2–4 stratose at base, strata progressively lost, unistratose above, unfertilised archegonia elevated on surface of calyptra.

Radula australiana occurs on mainland Australia (NSW, ACT, VIC), and in Tasmania and New Zealand, usually well above treeline in alpine or subalpine shrublands, grasslands and tussocklands where it grows in association with seepages and running water over and around exposed bedrock and boulders on alpine bluffs, rock outcrops and rock piles. However, Radula australiana also inhabits rocky open sites within forest habitats, particularly in Australia where high altitude Eucalyptus forest occurs in the alpine zone, and on bluffs associated with watercourses in New Zealand montane beech forest. Radula australiana is primarily a lithophyte on a wide range of sedimentary, metamorphic, and igneous rocks including greywacke and schist in New Zealand, and granite and basalt in Australia. Microsites occupied by Radula australiana are typically sheltered and shaded, such as the back walls of recesses in rock bluffs, crevices, between boulders within ephemeral streambeds. Radula australiana may also occur in bryophyte turfs on soil, usually in the shade of surrounding woody vegetation or rock. It shares all of these habitats with Radula helix, Herzogobryum teres, Nothogymnomitrion erosum, Cheilolejeunea mimosa, and Andreaea spp.

Radula australiana là một loài rêu trong họ Radulaceae. Loài này được K. Yamada mô tả khoa học đầu tiên năm 1982.