Frullania apiculata var. apiculata

Detailed description

Corticolous, plants olive-brown to reddish-brown, small to medium (600–1000 µm wide), forming a loose mat, creeping over, or intermingled with other hepaticae, occasionally closely adnate to substrate. Main stem to 30 mm long, 75–150 µm in diameter, to 11 cells wide; c.30 cortical cells + 60 medullary cells, cortical cells smaller than the medullary cells, cell walls firm, lumen irregularly shaped; outer 1–3 rows usually heavily thickened and pigmented red-brown. Branching Frullania-type, pinnate to bipinnate (occasionally tripinnate), 2–4mm long, obliquely spreading. Initial branching appendages vary, the first branch underleaf (BUL1) with three distinct segments, the ventral lamina divided 0.25 its length into two subequally sized lobes, the third dorsal segment saccate, sulcate, rarely explanate; the first branch leaf (BL1) either reduced in size, elobulate, with leaves characteristic of the main stem starting at BL3, or with two distinct segments, a strap-shaped dorsal segment + 1 saccate ventral segment (+ a stylus). Leaves of main stem variable: distant, contiguous, or densely imbricate; concave apices weakly to strongly incurved, apices minutely apiculate to 40 µm long; dorsal margin extending beyond the farther edge of the stem toward truncate or rarely rounded bases; surface smooth; margins entire. Lobules ± remote, to 150 µm, subparallel to obliquely spreading, cylindrical, ± uniformly inflated, slightly dorsiventrally appressed near mouth margin, 120–350 × 60–140 µm, rarely 1–2× as long as wide, lobule margins ± parallel. apex obtuse. Stylus filiform to narrowly foliaceous, 60–80 µm long. Underleaves of leading stems flat, obovate-cuneate to rarely suborbicular, bilobed (cut 0.3–0.4 of length), sinus narrowly acute V-shaped, lobes subtriangular, apices acute (rarely acuminate). Secondary branch lobules slightly smaller otherwise similar. Lobe median cells variable ranging from weakly to strongly thickened, pale yellow to subhyaline walls, with or without heavily pigmented, red-brown, secondary thickening, the trigones ± indistinct, confluent, subtriangular occasionally with intermediate thickenings onlonger walls, cell cavities to 25.0 × 12.5 µm, lobe basal cell walls thin, large, occasionally confluent, trigones subnodulose often with conspicuous intermediate thickening, basal cells several, larger than surrounding cells, cell cavities to 55 × 30 µm wide; lobe marginal cells subhyaline, irregular in shape, weakly to strongly thickened, cavities 6–10 × 5–8 µm. Underleaf median cells irregular in shape, trigones subhyaline, nodulose, confluent ocassionally distinctly convex. Lobule median cell walls sinuous, trigones confluent with nodulose intermediate thickening, cavities often c.2× long as wide, to 17 × 9 µm. Asexual reproduction, none recorded. Sexual structures not seen in Raoul Island specimens.