Allisoniella recurva R.M.Schust.
Allisoniella recurva R.M.Schust., Nova Hedwigia 22: 146. pl. 4: 7–11; 5: 12–13. 1972 (1971).
Holotype: New Zealand, North Is., Mt. Egmont, Schuster 48917a (herb. Schuster).
Plants rigid, light, translucent green to olive-green (but stems becoming pale brown with age) to pale brown throughout, the shoots 450–600 µm wide, to 2.2 mm high, at times contorted, not straight. Stems with cortex in a single layer of very thick-walled cells; medullary cells much larger, thin-walled. Leaves rigid, vertically oriented, stiffly and at times widely spreading to squarrose, contiguous to rather densely imbricate, the insertion transverse, the leaves 170–195 × 190–220 µm to 300–360 × 440–520 µm, bifid to (0.55)0.7–0.9, loosely conduplicate; lobes strikingly similar, markedly abaxially, broadly sulcate, erect but not incurved or if leaves squarrose then with lobes moderately incurved and weakly claw-like, variable in number of cells wide at base: (6)8–12 up to 19–28, the apex on sterile shoots acute and sharply pointed to subacute (and then terminating in a single cell or a uniseriate row of 2 cells) grading to narrowly rounded; sinus and margins strongly recurved, a distinct but abbreviated (0.2–0.3× leaf length) keel apparent that is often strongly arcuate or even semicircular. Cells subhyaline, with notably thickened, colorless walls, the marginal cells of lobes 10–11 µm wide × 12–17 µm long, the median lamina cells 12–16 µm wide × 14–19 µm long, hardly larger toward base; surface distinctly papillose, the papillae close and dense, notably evident in profile on leaf margins. Gemmae absent.
Plants autoecious. ♂ and ♀ Branches erect, from a common translucent brown, plagiotropic axis; ♂ branches ending in a spicate, tapered androecium (often with an intercalary branch from its base that is soon gynoecial); ♀ branches remaining simple, ending in a gynoecium, which often innovates, the innovation soon androecial. Perianths 4–5-plicate, the shallowly lobulate mouth fringed by strongly elongated (4–5:1) thick-walled cells, whose distal 0.2–0.35 are free to form finger-like extensions that are 7–10 µm wide basally × 30–38(40) µm long.
Sporophyte unknown.
Distribution and Ecology : Endemic to New Zealand: South Island (855–1480 m), North Island (670 m).
A species of upper montane forests and the alpine zone. Found creeping among flowering plants at the side of a cascading stream in a Nothofagus forest at 855–870 m (near South Branch of Borland Burn, Fiordland Natl. Park). Schuster (1996a) cited a specimen from a moist clay bank in a N. menziesii forest, growing mixed with Paracromastigum furcifolium and Isotachis (track to Hopurahine Falls, Waiotupukura River near Lake Waikaremoana, Urewera Natl. Park, ca. 670 m, leg. Schuster). Also occurring at the lip of a grassy area along the side of a seepage area at the margin of a tarn in a mosaic of tussock grass and alpine vegetation along with tarns, rills, rocky outcrops and boulderfields (Rainbow Skifield, St. Arnaud Ra., 1360–1480 m). The type is from Mt. Taranaki.
Comments : We have broadened the concept of this species to include populations that have variable lobe apices, some lobes terminating in a single cell or a uniseriate row of 2 subisodiametric cells, while others are commonly narrowly rounded (e.g., Engel 18692 from near the South Branch of Borland Burn, Fiordland Natl. Park). Another collection (Engel 22786 from Rainbow Skifield, Nelson Lakes Natl. Park) has leaf lobes mostly acute and often with a uniseriate row of 2 cells, but also has occasional lobes that are narrowly rounded and appear much like those of the Borland Burn plant. Such populations otherwise have characters typical of the species, i.e., a) deeply bilobed (to 0.7–0.9) leaves that are folded and have a distinct, recurved keel; b) strongly gibbous sinus bases; and c) a markedly papillose leaf surface. It should be emphasized that the shape and form of the leaf lobe apex no longer may be utilized as characters to distinguish Allisoniella recurva from A. nigra (cf. keys in Schuster, 1972a, 2002a).
The type was sparing and had only immature gynoecia, and, on that basis, the species was stated to be “Dioecious?” by Schuster (1972a). However, based upon study of more abundant plants, Schuster (1996a, p. 12) found the species to be “clearly autoecious.”
This taxon differs from all others in Allisoniella in the very conspicuously papillose surface (the papillae are readily evident when leaf profiles are examined) and more deeply bifid lateral leaves, usually divided to 0.7–0.9 and only sporadically to 0.6–0.65. The keel is usually concave, in part because the sinus is strongly decurved, and spreads at approximately right angles to the stem or is distinctly decurved. The stems have only a single layer of tangentially somewhat flattened cortical cells delimited; these cells are thick-walled and papillose on the thickened free walls.
The species is similar to the southern South American Allisoniella subbipartita (C.Massal.) R.M.Schust. & J.J.Engel in the pointed lobes, often ending in 2 superposed cells, and 1-stratose cortex, but that species has leaves 0.85–0.95 bifid and a smooth or obscurely papillose leaf surface.
