Isolembidium R.M.Schust.
Type: Isolembidium anomalum var. cucullatum (E.A.Hodgs.) J.J.Engel & R.M.Schust. Lembidium cucullatum E.A.Hodgs.)
Plants isophyllous, erect, plane or decurved to cernuous distally, green and opaque (olive-green in herb.), lacking conspicuous secondary pigments; shoots medium-sized, ca. 10–15 mm high, ca. 900–1050 µm wide. Branching frequent, irregular or regular, both intercalary and terminal; intercalary branches both ventral and lateral; terminal branches of Frullania and Microlepidozia types, issuing from distal sectors of shoots; older shoot-sectors conspicuously remote-leaved, with stems rhizome-like, extensively exposed and microphyllous—but a conspicuous system of geotropic stolons hardly developed (only occasional geotropic stolons seen). Stems with a distinct but not very pronounced hyaloderm that eventually collapses with age and 1–2 subepidermal layers of smaller, thick-walled, brownish cells and a medulla of numerous hyaline, rather leptodermous cells, the internal medullary cells larger. Rhizoids virtually absent. Leaves with insertion transverse to subincubous, broadly ovate-subrotundate to reniform-rotundate in outline, cucullate, nearly vertically oriented, obliquely to widely spreading above but appressed and ± clasping the stem toward shoot bases, firm, polystratose (median portions (2)3–4-stratose, only the margins thinner and gradually 1-stratose); apices undivided, variable: broadly rounded to repand to denticulate-dentate; margins entire. Cells firm, with walls thin to faintly thickened, but trigones conspicuous, although concave- to flat-sided; cells at leaf apex and often also along margins enlarged, hyaline, often eventually collapsing and then resulting in an erose condition; surface striolate-papillose. Oil-bodies absent in inflated cells at leaf apex, otherwise present in some cells while absent in others, occupying a very small portion of the cell lumen, smokey pale grey or hyaline, typically 1–2 (rarely 3–4) per median leaf cell, smooth and appearing without texture or finely and faintly granular, appearing nearly smooth, but obscurely and suggestively segmented (obscurely 3–4-segmented fide Schuster and Engel, 1987b), globose to narrow ovoid to narrowly to broadly elliptic to ± crescentic, 1.9–2.4 × 2.4–3.8 µm to, less often, 2.4 × 4.8 µm, spherical ones 2.9 µm in diam., the oil-bodies rather soon breaking up and, with breakup, becoming irregular, the surface appearing papillose and with discrete spherules. Chloroplasts large for cell size. Underleaves identical to leaves. Asexual reproduction lacking.
Androecia lateral- or ventral-intercalary in origin, basal, from leafy axes or microphyllous stolons, compactly spicate, julaceous, microphyllous, small, only 350–450 µm wide; bracts small, concave, rather boat-shaped, strongly inflated throughout, with sides folded together, the apex bluntly acute (when not flattened), undivided and entire; margins entire; antheridia 1 per bract, the stalk 2-seriate; bracteoles vestigial or reduced to few-celled remnants bearing several clavate slime papillae at apex, lacking antheridia. Gynoecia on abbreviated ventral-intercalary branches lacking normal leaves, the branches originating from lower sectors of upright leafy shoots; bracts and bracteole identical, erect, together tube-like and tightly ensheathing the lower sector of the perianth, deeply concave, much larger than leaves, elliptic to lingulate, the apex rounded to retuse, often with several slime papillae, the lamina margins with several slime papillae. Perianth exceedingly slender, terete below but trigonous above, very long (to 11.8× longer than wide) and extremely attenuated, narrow-fusiform, plicate toward the contracted, ± pointed apex, the mouth shallowly lobulate and crenulate with narrow, often curved cells that are barely free at the tips, the cells striolate-papillose.
Capsule long-cylindrical, the wall 4-stratose, 41–42 µm thick; outer layer of cells equal to thickness of 1.9–2.5 of interior strata, the radial walls with continuous sheets of magenta wall material plus weak nodular thickenings on both faces of alternating longitudinal walls; innermost layer of cells with semiannular bands, the bands thick, usually complete, the radial walls otherwise with continuous sheets of magenta wall material.
Spores 14.4–16.8 µm in diam., pale brown, with dense, low, but sharply defined papillae and short-vermiculate markings. Elaters rigid, nearly straight, bispiral, 11–13 µm in diam., the spirals 3.8–4.8 µm wide.
The genus is Australasian and has a single species with two varieties, both present in New Zealand.
References: Schuster and Engel (1987b; mon.); Schuster (2000a).
