Cephaloziella exigua R.M.Schust.
Cephaloziella exigua R.M.Schust., Nova Hedwigia 63: 49. f. 11. 1996.
Holotype: New Zealand, South Is., Milford Sound, along trail from hotel to Bowen Falls, sea level, Schuster 48602.
Plants straggly, creeping as isolated, sinuous stems among Herbertus, lacking secondary pigmentation above or the leaves at shoot tips intensely vinaceous, the stems whitish above but with age weakly brownish, minute, the shoot with leaves little broader than stem alone, to, at most, 90–100 µm wide with leaves; shoot apices terete, the minute leaves distally overarching shoot apex, concave and erect-appressed like lower leaves. Branching sparing and irregular, the branches all intercalary, ventral and (?)lateral, widely spreading, almost immediately similar to parent axis in diameter. Stems rigid and rather wiry, whitish and translucent above, with age faintly brownish, the cortex in 1(2) layers of exceedingly thick-walled cells, the cortex in surface view with rounded to elliptical lumina only 3.4–7.5 µm wide × 12–18 µm long. Leaves erect-appressed, closely adnate to stem (the distal portions of lobes weakly erect-spreading, but the sharp lobe tips then again incurved), on older shoot sectors leaves hyaline and so closely applied to stem as to be almost imperceptible; leaves exceedingly remote, the spaces between leaves 3–6× as long as leaves, transverse, tending to be asymmetrical, with the ventral half somewhat ampliate, the leaves reniform to broadly quadrate-rounded in outline (but outline almost impossible to decipher, since the tiny leaves can hardly be dissected free), to 75–80 µm wide × 55–62(72) µm long, always a little to much wider than long, bilobed to ca. 0.5–0.6, the leaf margins serrulate with apices of projecting cells; lobes equal, sharply pointed, the prominent end cell with tip strongly thick-walled, often inserted on a strongly transverse to crescentic cell, the lobes (3)4(5) cells broad at base, the margins serrulate-crenulate with the thick-walled tips of conspicuously projecting cells; lamina 2–4 cells high from sinus base to leaf base, 8–9 cells wide. Cells of the ± hyaline shoot apices locally with intense vinaceous-pigmented walls, but in mature shoot sectors, the leaves decolorate and transparent; cells thick-walled, with maturity very thick-walled and with lumina rounded, becoming guttulate, at lobe bases from 8–11 × 10–14 µm, to locally, 10–12 × 12–19 µm; surface smooth. Underleaves reduced to a slime papilla or, occasionally, a stalked slime papilla, at most formed of 2 superposed cells. Gemmae lacking.
Otherwise unknown.
Distribution and Ecology : Endemic to New Zealand: South Island (sea level). Known only from the type, which was found creeping between shoots of Herbertus oldfieldianus over seepage-wet rocks, and admixed with Acromastigum brachyphyllum, Adelanthus occlusus, Anastrophyllum schismoides, Cheilolejeunea spp., Cryptochila pseudocclusa, Goebeliella cornigera, Lepicolea, Trichotemnoma corrugatum, Heteroscyphus (=Tetracymbaliella) and other taxa.
Comments : Perhaps the smallest hepatic ever found, with leafy shoots only 90–100 µm in diam. and “far smaller than any other Cephaloziella ” (Schuster, 1996a, p. 53). Shoots are thread-like, with very remote, closely appressed, scale-like, relatively few-celled leaves. The stem cortical cells in surface view are guttulate with exceedingly thick-walled cells with rounded lumina.
