Isophyllaria attenuata (Rodway) E.A.Hodgs.
Isotachis attenuatus Rodway, Tasman. Bryoph. 2: 62. 1916.
Isophyllaria attenuata (Rodway) E.A.Hodgs., J. Roy. Soc. New Zealand 2: 111. 1972.
Type: Tasmania, Mt. Wellington Plateau.
Holotype: New Zealand, Stewart Is., Mt. Allen, Feb. 1949, Murray 2193 (MPN ex herb. Hodgson 11720).
Plants with branches mostly ventral-intercalary; Frullania -type branches rather common but less abundant than intercalary branches. Leaves 320–400 µm wide × 620–760 µm long, bifid to 0.65–0.75; lobes narrowly lanceolate, plane or weakly abaxially sulcate (except at apices), terminating in a uniseriate row of 2–4 subisodiametric cells, often with a number of biseriate tiers basal to the uniseriate row, the ultimate row of cells of the lobes + the cells of uniseriate row each with a biconvex thickening of the exposed wall (depending on the plane of focus but seen at least in profile), the inner portion of the lenticular thickening often occupying a distinct volume of the cell lumen, the uniseriate portion often submoniliform; disc marginal cells with sublenticular thickenings as in lobes. Cells of leaf with middle lamella distinct, the cells in median sector of disc 13–16 µm wide × 22–35 µm long. Oil-bodies occurring throughout leaf, occupying a small portion of cell lumen, dull and opaque, faintly greyish, 2–4 per median cell of lamina, the number the same throughout leaf, obscurely and faintly coarsely granular, appearing roughened, the granules slightly protruding beyond the membrane, the oil-bodies mostly globose and 2.5–4 µm in diam., less often broadly elliptic and 2.9 × 3.8–4.6 µm. Chloroplasts large for cell size.
Gynoecia with bracts and bracteoles gradually grading in size to vegetative leaves, those of innermost series similar in form to leaves and underleaves but larger and distinctly concave, cuneiform from a narrow base, the lobes often twisted, with recurved margins, shallowly sulcate, the lobe and lamina margins entire. Perianth at most 0.35 exserted, at times barely exserted beyond bracts, ovate to short-elliptic in outline, bluntly trigonous in distal half or a little more, shallowly plicate distally, weakly narrowed to the rather wide and open, at times slightly contracted mouth; mouth irregularly dentate, the teeth small, thick-walled and with a striate-papillose surface, often consisting merely of a uniseriate row of 2 cells or a biseriate tier + a single cell, occasionally with 2 biseriate tiers + a uniseriate row of 2 cells, the terminal cell at most slightly longer than wide, tapered to a rounded summit.
Seta with an outer row of 16 cells surrounding an inner core of 9 somewhat smaller cells with straight to bulging corner thickenings. Capsule spherical, the walls fragile and easily fragmenting, in 3 layers, 30–35 µm thick; outer layer thicker than inner layers combined, the outer layer of cells subquadrate to short- (both transversely and longitudinally) rectangular, walls moderately thickened, the longitudinal and transverse walls with vinaceous nodular thickenings; innermost layer of cells variable in shape and short- to long-subrectangular, the walls ivory-white and moderately to markedly thickened, with vinaceous sinuous-nodular thickenings, a thin, sheet-like, vinaceous-pigmented thickening often also present on the radial between the nodular thickenings, semiannular bands lacking.
Spores 12.5–14.4 µm in diam., red-brown, with low but sharply defined, dense, vermiculate markings that often anastomose + some papillae. Elaters tortuous (often merely C-shaped), 6.7–8.2 µm wide, gradually tapered toward the tips, bispiral throughout or bispiral in median sector and unispiral at the ends, the spirals 2.9–3.8 µm wide.
Distribution and Ecology : New Zealand: Campbell Island, Auckland Islands, Stewart Island (750–960 m), South Island (1050–1970 m), North Island (520–1700 m); Australia: Tasmania. In New Zealand known from Rakiura (Mt. Allen, Mt. Anglem), Fiordland (Mt. Burns, Eldrig Peak, Lake Wapiti, Gertrude Valley), Westland (Upper Otira valley), Western Nelson (Mt. Euclid) and Volcanic Plateau (Mt. Ruapehu, Waimiha Stream) EPs.
The species usually occurs in the alpine zone where it may be found on moist or at times irrigated exposed rock and in snow-melt stream courses, granite and greywacke in the South Island and Stewart Island, or volcanic rock on Auckland and Campbell islands and Mt. Ruapehu. For example, it occurs at 1940–1970 m in seepage over rock domes at the head of Gertrude Valley, Fiordland Natl. Park. Invariably it has been found accompanied by Hepatostolonophora rotata var. perssonii, but is also found with Allisoniella scottii, Blindia robusta, Cephalomitrion aterrimum, Cryptochila acinacifolia, Isotachis intortifolia, Pachyglossa tenacifolia, Rhacocarpus purpurascens, Riccardia aequicellularis and R. aequitexta.
Comments : The species should not confused with a ny other except perhaps small, deeply pigmented phases of Herbertus, a plant that, like Isophyllaria, is isophyllous with both leaves and underleaves deeply bifid, and that has frequent ventral-intercalary branching. Plants of the much smaller Isophyllaria, however, may be differentiated by the leaves being less imbricate on the stem, the evenly and markedly thick-walled cells, the weakly defined vitta and the symmetric, dorsally assurgent, stiffly spreading leaves with incurved, arched lobes vs. the presence of massive trigones separated by narrow, thin-walled places, the sharply defined vitta and the asymmetric, ventrally secund leaves in Herbertus.
