Psiloclada Mitt.
Psiloclada Mitt. in Hook.f., Bot. Antarc. Voy. 2: 143. 1855.
Lepidozia subg. Apiculo-lepidozia S.W.Arnell, Bot. Not. 107(4): 429. 1959.
Type: Psiloclada clandestina Mitt.
Plants wiry, loosely prostrate to somewhat ascending, dull, olive-green to brownish green, minute. Branching irregularly pinnate to rather regularly (but not especially closely) 1–2-pinnate, the branches of the Frullania type, oriented at ± 90° to main axis; ventral-intercalary branches occasional, often becoming flagelliform. Stem rigid, rather large for plant size, the cortex ill-defined, of notably thick-walled cells that grade into the thick-walled medullary cells, the medullary cells somewhat less thick-walled toward the central portion. Leaves remote to ± contiguous, hand-like and cupped: the disc and lobe bases stiffly spreading laterally, the terminal setiform cells each erect and oriented at ± right angles to the disc or aligned toward stem, the leaf insertion transverse in dorsal half and attaining the stem midline, distinctly succubous in ventral half; leaves weakly to strongly asymmetrically obtrapezoidal, 5–9(10)-lobed to 0.6–0.8; branch leaves with 1(2) fewer lobes. Lobes asymmetric, the ventral lobe(s) larger than the dorsal, the lobe bases each comprised of a few, thick-walled cells similar to those of the disc, the lobes each ending in a single, stiff, setiform, finger-like, hyaline, echlorophyllous, thin-walled cell, 11–12 µm wide × 40–65 to 85–110 µm long. Disc asymmetric, 1–2 cells high dorsally, 3–5 cells high ventrally. Cells of disc and lobe bases densely chlorophyllose, thick-walled; surface smooth. Oil-bodies absent. Underleaves remote, 3–6(8)-lobed, the disc stiffly spreading (often at right angles to the stem), the setiform cells each strongly erect and oriented parallel to stem or arched toward the stem, the lobes consisting solely of a single hyaline, elongate, setiform cell or of 2 cells, then the terminal setiform cell subtended by a subisodiametric cell; disc usually 2 cells high. No asexual reproduction.
Dioecious (but often sterile). Androecia on short, determinate, ventral-intercalary branches from leading shoots; bracts 4-lobed to ca. 0.5, the terminal cell very long and narrow; antheridia 1–2 per bract, the stalk uniseriate; bracteolar antheridia lacking. Gynoecia on abbreviated ventral-intercalary branches from main stem, the gynoecium base narrowly stipitate (with a rudimentary perigynium) and rhizoidous, the gynoecium with 1–2 series of bracts and bracteoles, the innermost ± ovate, irregularly 2–4-fid for 0.5–0.7 their length, the disc broadly orbicular-quadrate; lobes acuminate-caudate, ending in 1–3 exceedingly elongate cells. Perianth narrowly fusiform to slenderly ovoid, terete below, trigonous above, distinctly pluriplicate distally, ± gradually narrowing to the contracted mouth; mouth fringed with ± tortuous cilia consisting of a single elongate cell or a uniseriate row of 2 elongate cells and, immediately below, 1–2 biseriate tiers comprised of laterally connate cells free at their apices, the cilia also with a few accessory shorter teeth below; perianth 2–4-stratose in basal sector.
Seta with 8 rows of outer cells surrounding an inner core of 13 much smaller cells. Capsule short-ellipsoidal, the wall 2(very locally 3)-stratose; outer layer of cells with two-phase development, the longitudinal walls with thin, sheet-like thickenings and feebly nodule-like swellings (lending the vertical walls a sinuous-nodular appearance) alternating with walls that are devoid of thickenings; inner cells longer and narrower, for the most part with rather nodule-like to spine-like thickenings, sporadically tangentially extended and then with incomplete to complete semiannular bands.
Spores 11–14 µm in diam., vermiculate-irregularly areolate. Elaters 8.2–12.5 µm wide, bispiral.
Psiloclada is likely a monotypic genus, with a single, variable, broadly distributed species that may be subdivided into three subspecies (Schuster, 1980a, 2000a). Subspeciesclandestina occurs in New Zealand, Tasmania and Australia; subsp. melanesica R.M.Schust. is found in New Guinea, New Caledonia, the Solomon Islands and Fiji (and ?Amboina); and subsp. spinosa (S.W.Arnell) R.M.Schust. is disjunct in South Africa (Arnell, 1954, type of Lepidozia spinosa; 1963). The status of P. unguiligera Schiffn. of Indonesia, Melanesia and the Philippines is uncertain and may be the same as subsp. melanesica.
References: Fulford and Taylor (1959); Engel (1985); Schuster (1980a, 2000a).
