Acromastigum verticale (Steph.) E.A.Hodgs.
Bazzania verticalis Steph., Hedwigia 32: 214. 1893.
Mastigobryum verticale (Steph.) Steph., Sp. Hepat. 3: 449. 1908.
Acromastigum verticale (Steph.) E.A.Hodgs., Trans. Roy. Soc. New Zealand 82: 18. 1954.
Type: New Zealand, “ leg. Prof. Kirk inter No. 373” (G!).
Acromastigum martinii E.A.Hodgs. in W.Martin, Trans. Roy. Soc. New Zealand 78: 496, 499. 1950, nom. nud.
[Fig. 85: 4, oil-bodies, p. 394; Fig. 86]
Plants weakly anisophyllous, ± isophyllous in less robust sectors (common) of shoot, suberect, rigid, appearing fleshy, light green, nitid when dry; shoots small, to 1.2 mm wide. Branching infrequent, regularly of Frullania type; branch half-leaf ± symmetric, ovate, undivided, nonvittate, tapering to a narrow apex; first branch underleaf undivided, broadly ovate, inserted on ventral-lateral side of juncture of main axis and branch. Acromastigum -type branches common, stoloniform, rather short, the half-underleaf resembling the half-leaf of a Frullania -type branch. Stem cortical cells moderately differentiated, in 12–16 rows, the outer tangential wall thick-walled, the radial walls thin or slightly thickened, the cortical cells moderately larger than the slightly to moderately thick-walled medullary cells. Leaves rigid, vertical or nearly so, not dorsally assurgent, squarrose at least at base, with the narrowed distal sector of the leaf erect or hooked at the tip, approximate to loosely imbricate, moderately concave; leaves subvittate, 595–700 µm wide × 560–665 µm long, transversely to feebly incubously inserted and oriented; leaves variable in shape, somewhat asymmetrically triangular-ovate, with a broad base, acuminate, the apex narrowly acute, undivided or at times retuse or shallowly and equally or unequally 2(3)-fid (if 3-fid, the dorsal-most tooth at times displaced on dorsal margin and lower); margins entire, a pellucid border lacking, the dorsal margin ampliate and broadly cordate at the base, the ventral somewhat less so. Cells of leaf moderately thick-walled, with massive, nodular, knot-like trigones, the subapical cells 23–28 µm wide × 25–35 µm long, the median-basal cells much larger and elongate-rectangular, forming a broad subvitta, the subvitta cells 29–34 µm wide × 41–55 µm long, uniformly thick-walled, with less distinct trigones, the subvitta somewhat ventrally displaced; cells of the ampliate lateral and basal sectors ± isodiametric; marginal row of cells in lower half of leaf forming an indistinct border, the cells ± transversely elongate, their free walls strongly thickened; surface smooth throughout. Oil-bodies occupying a small portion of cell lumen, hyaline and somewhat glistening, with a milky appearance, (1)2 per median leaf cell, subglobose to broadly elliptic, finely and somewhat obscurely papillose, the spherules slightly protruding beyond membrane. Underleaves undivided, about as wide as stem or slightly wider, somewhat smaller than the leaves, ± subsymmetrically ovate (sometimes broadly so and then suborbicular), subvittate (but less so than leaves), the apex irregularly truncate or feebly notched at insertion of the 3 slime papillae; cells as in leaves; margins entire; surface smooth.
Capsule (fide Grolle, 1964h) with wall 3-stratose; outer wall with two-phase development, the longitudinal walls with sheet-like thickenings and distinct knot-like thickenings alternating with walls that are devoid of thickenings, the transverse walls devoid of thickenings or sporadically with an isolated nodule; innermost layer of cells narrowly rectangular, with 2–3 usually complete semiannular bands per cell.
Distribution and Ecology : New Zealand: Stewart Island (500 m), South Island (700 m), North Island, from only a few sites; Australia: Tasmania. On Stewart Island it occurs on moist, sandy soil at the head of Crooked Reach, Port Pegasus (leg. Martin) and from a creek bed (also Port Pegasus, leg. Scott); also known from the Tin Ra. in a penalpine meadow (leg. Schuster, Scott & Taylor, MPN) and from the walls of an incised stream (N of Mt. Allen, 500 m). On Stockton Plateau at 700 m, where it formed pure cushions of erect stems 10 cm deep in shallow water on an open streambed with sandstone bedrock and gravel bottom, surrounded by low Leptospermum scoparium scrub; accompanying species were Adelanthus falcatus, Blindia robusta, Cheilolejeuneaaff.mimosa, Isotachis montana, Pachyglossa tenacifolia, Riccardia australis and Stigonema sp. (a cyanobacterium). The type is from Great Barrier Island.
Comments : Distinct from other New Zealand species of the genus in the subvittate, triangular-ovate leaves and the abruptly narrowed, erect to inflexed leaf apices. In addition, the characteristic pellucid leaf margin, seen in varying degrees in all other New Zealand Acromastigum species is lacking in A. verticale. The only species likely to be confused with A. verticale is A. cavifolium, but this species has ± homogeneous areolation and more narrowly ovate leaves, with a broadly rounded to truncate apex. Also, the stem of A. verticale has a somewhat fleshy appearance, with a cortex of short, isodiametric, rather thin-walled cells as seen in surface view. For additional distinctions, see under A. cavifolium.
