Flora of New Zealand Series

Acromastigum brachyphyllum A.Evans, Ann. Bryol. Suppl. 3: 60. f. 12. 1934. 

Holotype: New Zealand, South Is., Paparoa Ra., 3000 ft., R. Helms (Y!); isotype: (CHR 4948 ex herb. T. Kirk 251!).

[Fig. 85: 3; Fig. 92]

Plants rigid and wire-like, in loose tufts or mats, the leaves yellowish to golden brown but often ± rust-colored basally, the stems reddish brown, the plants nitid when dry; shoots small, to 0.6 mm wide. Branching sparingly pseudo-dichotomously furcate or clearly lateral, of Frullania type, widely spreading; branch half-leaf ± symmetric, very wide ovate, undivided, tapering to a sharp apex (rarely bidentate), subauriculate at the base, with a median-basal field of larger cells; first branch underleaf 2-lobed, inserted on ventral-lateral side of juncture of main axis and branch. Acromastigum -type ventral branches occasional, stoloniform. Stem cortical cells in 7 rows, the radial and outer tangential walls very thick, the transverse walls thin, the cortical cells larger than medullary cells, in surface view the dorsal cortical cells large, sinuate-hexagonal, the ventral cortical cells smaller. Leaves small in proportion to stem, rigid, fragile, easily tearing, cochleariform, distant to contiguous, with much of stem exposed in dorsal aspect, obliquely spreading, when dry strongly ventrally deflexed and cupped, when moist moderately convex, the lobe tips deflexed and not visible in dorsal aspect, with scattered bistratose patches (at most in groups of 3–5 cells), frequently in the median dorsal sector, subvittate, 245–400 µm wide × 320–465 µm long, strongly incubous, asymmetrically orbicular-ovate; apex unequally bilobed to ca. 0.25, the ventral lobe longer and broader than the dorsal, the lobes acute to obtuse, terminating in a single cell or 2 superposed cells, entire; dorsal lobe 4–6 cells wide at base; ventral lobe 4–5 cells wide at the base, 2–4 cells long; dorsal margin strongly ampliate, cordate to ± auriculate at base, extending to middle of stem or somewhat beyond, entire or somewhat irregularly repand-denticulate at the base, sometimes with several large, spherical slime papillae; ventral margin nearly straight, entire, not decurrent. Underleaves small, about equal to the stem in width, distant, squarrose at base and becoming erect, slightly convex, broadly elliptic, ± equally 3-lobed to ca. 0.3–0.5, subequal or the median lobe smaller; lobes closely approximate, 4–7 cells wide at base, the apex rounded to truncate, entire, terminating in 2–4 laterally juxtaposed cells and ending in a spherical slime papilla; disc margins cordate to subauriculate, narrowing abruptly to the insertion; cells of disc and lobes strongly thick-walled; margins entire; surface smooth. Cells of leaf distinctly thick-walled, those of ventral sector of leaf larger, forming an indistinct vitta (subvitta) that is strongly ventrally displaced, the cells strongly thick-walled, with bulging, knot-like, often confluent trigones; cells of vitta 25–30 µm wide × 30–40 µm long; cells of the ampliate dorsal sector much smaller, ± evenly thick-walled, 7–13 µm wide × 12–14 µm long; surface smooth throughout. Oil-bodies in the vitta cells occupying a conspicuous portion of the cell lumen, pale smokey grey, 2–3(4) per cell, very coarsely botryoidal, the segments very thin and membranous, the segmentation irregular and uneven, with age the individual spherules considerably swollen and the oil-bodies becoming fewer segmented and ultimately smooth; nonvittate cells and distal cells of lobes with oil-droplets only.

Androecia and gynoecia not seen.

Distribution and Ecology : Endemic to New Zealand: South Island (320–540 m). Known only from Westland (Omoeroa Saddle) and Western Nelson (Paparoa Ra. and Stockton Plateau) EPs.

The Omoeroa Saddle collection is from peaty soil in Lagarostrobos colensoi – Phyllocladus alpinus shrubland with Carpha alpina and Sphagnum cristatum at 320 m. Accompanying species are Adelanthus falcatus, Riccardia and Clasmatocolea. The Stockton collection is from a wet overhanging bank under stunted Nothofagus solandri var. cliffortioides – Phyllocladus alpinus forest at 540 m, with Acromastigum verticale.

Comments : We know of no other Acromastigum with leaves at least locally bistratose (Fig. 92: 8–10). The presence of the bistratose condition in this species requires careful assessment, especially when compared to presence of that character in smaller phases of A. anisostomum. The species looks very similar to A. anisostomum in color and size of the plants, and further work needs to be done to establish its differentiation from that species.