Acromastigum anisostomum (Lehm. & Lindenb.) A.Evans
Jungermannia anisostoma Lehm. & Lindenb. in Lehm., Nov. Min. Cogn. Stirp. Pug. 6: 57. 1834. Mastigobryum anisostomum (Lehm. & Lindenb.) Gottsche, Lindenb. & Nees, Syn. Hepat. 219. 1845. Bazzania anisostoma (Lehm. & Lindenb.) Trevis., Mem. Reale Ist. Lombardo Sci. Lett. III, 4: 414. 1877. Acromastigum anisostomum (Lehm. & Lindenb.) A.Evans, Ann. Bryol. Suppl. 3: 48. 1934.
Type: New Zealand, South Is., Dusky Bay, [Menzies], “Hb. Hooker” (STR!).
Jungermannia atro-virens Hook.f. & Taylor, London J. Bot. 3: 388. 1844.
Mastigobryum atro-virens (Hook.f. & Taylor) Gottsche, Lindenb. & Nees, Syn. Hepat. 218. 1845.
Bazzania atro-virens (Hook.f. & Taylor) Kuntze, Revis. Gen. Pl. 2: 832. 1891.
Type: Auckland Is., ex herb. Jack (G!).
Acromastigum anisostomum var. minutum E.A.Hodgs., Trans. Roy. Soc. New Zealand, Bot. 3: 71. 1965.
Holotype: Stewart Is., near Cedric Creek, N. W. Arm, Paterson’s Inlet, 29 Jan. 1949, Martin (herb. Hodgson no. 12151) (MPN!).
Plants stiff and wire-like, in pure colonies or mixed with other bryophytes, suberect to erect, yellowish to reddish brown (the stem often becoming deep red to blackish); plants when dry distinctly nitid and with leaves strongly ventrally deflexed; shoots small, to 0.8 mm wide. Branching pseudo-dichotomously furcate, the branches of Frullania type, widely spreading; branch half-leaf ± symmetric, ovate, undivided, vittate, tapering to a sharp apex; first branch underleaf 2–3-lobed, inserted on ventral-lateral side of juncture of main axis and branch. Acromastigum -type branches frequent, long and stoloniform. Ventral-intercalary branches lacking. Stem stiff and brittle, the cortical cells strongly differentiated, much larger than the medullary cells (ca. 2:1), in 7 rows, the radial walls thick-walled, the outer tangential walls also thickened, at times strongly so; medullary cells thinner-walled. Leaves rigid, imbricate, allowing little of stem exposed in dorsal aspect, spreading (ca. 60–80°), moderately convex, the apex moderately deflexed but the ventral lobes of opposing leaves not overlapping one another in ventral aspect; leaves vittate, 215–300 µm wide × 385–600 µm long, strongly incubous, asymmetrically ovate; apex unequally bilobed to ca. 0.2–0.35(0.45), the ventral lobe ca. 2× or less the dorsal in length, the lobes entire, terminating in a single cell or uniseriate row of 2 non-elongated cells; dorsal lobe acute, 5–7 cells wide at base; ventral lobe narrowly acute, 4–6 cells wide at the base and gradually tapering to the tip; dorsal margin ampliate, with a blunt tooth or rounded to subrectangular auricle at base, the basal sector often also with 1–2 slime papillae and a blunt tooth, the margin otherwise entire and extending to middle of stem or somewhat beyond; ventral margin nearly straight or somewhat incurved, sporadically subauriculate at base, entire. Cells of leaf distinctly thick-walled, those of ventral sector of leaf distinctly larger, forming a strong vitta running parallel to and 2–4 cells within the ventral margin; vitta 3–4 cells wide at base (or more in leaves with a ventral dilation), the cells with bulging to knot-like, often confluent trigones, 21–30 µm wide × 28–44 µm long; cells in dorsal sector of leaf much smaller, 12–18 µm wide × 15–21 µm long, uniformly thick-walled, without trigones; surface smooth. Oil-bodies (fide Schuster, 2000a, fig. 111) (2)4–8(16) per vitta cell, coarsely botryoidal, at times few segmented or homogeneous and smooth, 4–7 × 4–17 µm. Underleaves small and inconspicuous, distant, ± squarrose at base and becoming erect, convex, broadly elliptic to subrectangular, broader than long, deeply and ± equally 3-lobed to ca. 0.5; lobes 4–6 cells wide at base, the apex broadly rounded to retuse, entire, terminating in 2–4 laterally juxtaposed cells; disc margins somewhat ampliate, narrowing abruptly to the insertion, entire; cells of disc and lobes strongly thick-walled; surface smooth. Fungal partner absent.
Androecia and gynoecia not seen.
Distribution and Ecology : New Zealand: Auckland Islands, Stewart Island (530 m), South Island (0–900 m), North Island (300–900 m); Australia: Tasmania, New South Wales. Known from Fiordland, Westland, Western Nelson, Southern North Island (Ruahine and Tararua ranges), Auckland (Coromandel, Little Barrier Island) and Northland (Waipoua) EPs.
This species, which at times may become locally abundant, often forms deep, pure, golden brown, intricately interwoven mats or mounds over peaty substrates, on decayed stumps and logs (particularly those that are bryophyte covered) and peaty ground in general, where not apt to be submerged. Regularly accompanying species in these habitats are Adelanthus falcatus, Anastrophyllum schismoides, Bazzania nitida, Dicranoloma robustum, Hymenophyllum armstrongii, Kurzia hippuroides and Wijkia extenuata.
Other species that are less often seen in association are Acrobolbus lophocoleoides, Archeophylla schusteri, Chandonanthus squarrosus, Clandarium xiphophyllum, Ditrichum difficile, Heteroscyphus cymbaliferus, H. decipiens, Lepicolea attenuata, Lepidozia kirkii, L. setigera, Pulchrinodus inflatus, Radula scariosa and Schistochila ciliata. Sometimes on tree bases mixed with Acromastigum cavifolium, Herbertus oldfieldianus and Lepicolea, and rarely epiphytic and with Acrochila biserialis, Herbertus oldfieldianus and Hymenophyllum armstrongii. It occasionally occurs in scattered to dense patches over bedrock (e.g., ca. 800–840 m in a protected valley below summit area of “Little Moehau,” Coromandel Peninsula). On Stewart Island at 530 m in mosaic communities of dense heath-forming shrubs to 3 m tall, penalpine herbs, and dwarf heaths to 0.5 m tall, dominated by stunted Leptospermum scoparium and Dracophyllum and a ground tier including Empodisma minus. Accompanying species in semi-open habitats are Anastrophyllum schismoides, Campylopus clavatus and Kurzia hippuroides.
Comments : Despite the considerable variation in vigor and leaf form in Acromastigum anisostomum, this species is clearly separable from A. mooreanum, which has a much narrower, stiff, spur-like, lanceolate ventral leaf lobe vs. a shorter, more triangular ventral lobe in A. anisostomum. The leaves of the two species are otherwise very similar. In A. anisostomum the vitta is 2–3 cells wide and formed of cells that diminish in size from leaf base to apex. The cells are up to 35 × 50–65 µm basally, 28–32 × 45–55 µm subbasally and only 25–30 × 30–38 µm above and to either side. The cells along the ventral margin are smaller, but not nearly as small as in the anterior half of the lamina, where they become progressively smaller and average only 12–13 µm along the anterior leaf margin. The vitta cells have coarse trigones and thick longitudinal walls, but the transverse walls between successive cells are relatively thin. On either side of the vitta, the cells become more nearly equally thick-walled, with rounded rather than irregular and sinuous lumina.
