Bazzania subtilis Trevis.

Bazzania subtilis (Sande Lac.) Trevis. (Fig. 14) Memorie del Reale Istituto Lombardo de Scienze e Lettere 4 (13): 414 (Trevisan 1877). — Mastigobryum subtile Sande Lac., Annales Musei Botanici Lugduno-Batavi 1: 302 (Sande Lacoste 1864). — Types: Java, Teysman s.n.; Sumatra, Korthals s.n. (lectotype: L[Sumatra, Korthals s.n], fide Meijer 1960, not seen). MATERIAL EXAMINED. — New Caledonia • North Province, Hienghène, Mt Panié massif, Payolé; litter on roots, cloud forest, mica schists massif; 1400 m; 9.X.2012; Thouvenot NC2497 • Poindimié, Amoa valley, below Goro Até Mèkébo; on bark in cloud forest, volcano-sedimentary massif; 721 m; 12.X.2019; Thouvenot NC2658 • South Province, Sarraméa, Dogny massif, along the path to Dogny Plateau; on dead wood in wet forest; 23.IX.2008; Thouvenot NC1713 • La Foa, Dogny Plateau; on laterite in wet forest; 950 m; 24.X.2019; Thouvenot NC2674 • ibid.; on dead wood; Thouvenot NC2629, NC3407 • Païta, Humboldt Massif, path to the hut; on tree fern stipe; 1255 m; 1.X.2008, Thouvenot NC3469. DISTRIBUTION IN NEW CALEDONIA. — Present in both provinces of the main island (Grande Terre). TOTAL RANGE. — Australia (Meagher 2019), Java, Sumatra, Borneo (Meijer 1960), Papua New Guinea (Grolle & Piippo 1984), Malaysia (Cheah & Yong 2016), New Caledonia. DESCRIPTION Plants Fragile, small and soft, decumbent, forming loose wefts; shoots complanate both in dry and wet condition, 1.5- 2.0 mm wide, stems (0.15-)0.20(-0.27) mm wide; terminal branching common, pseudo-dichotomous, ventral-intercalary branches common, usually flagelliform, but normal leaved branches may arise ventrally at underleaf axils. Leaves Contiguous, spreading, hardly convex, leaf bases more or less imbricate, dorsal insertion reaching the stem midline, at most the dorsal leaf bases hiding the stem, leaves 0.65-1.05 mm long, 0.33-0.55 mm wide near bases, 0.18- 0.35 mm below apices, asymmetrically ovate-oblong to ovate-lingulate, not falcate, length-width ratio 1.5-2.4; cuticle smooth or slightly verrucose, especially at margins and apices, margins usually crenulate-denticulate, the dorsal ones widely convex, the ventral slightly concave or sub-straight; apices variously dissected even in a same plant, typically obliquely truncate, 3-dentate, teeth shortly linear to narrowly triangular, 2-4 cells long, but some ones often wider and shorter or apices may be just unevenly crenulate-dentate. Cells Central basal cells forming a conspicuous subvitta made of 5 (-7) files of longer and wider cells, surrounded by 1-2 files of smaller transitional cells; median cells rounded-oblong, 12-25 µm wide, 12-30 µm long, usually thick-walled with inconspicuous trigones, more rarely firm walled with medium acute trigones; marginal cells smaller with thicker and verrucose free walls, oblate on ventral side, rounded-oblong on dorsal margin; internal cells oblong to rectangular, 25-40 µm wide and 30-70 µm long, thin-walled with large acute trigones. Underleaves Patent, slightly down curved, positioned close to the leaf bases on one side of the stem, then very narrowly connate if any, small, sub-quadrate to longer than wide in outline, 0.23-0.55 mm long, 0.28-0.48 mm wide, 1-2 times wider than the stem; lateral margins convex or lobulate with widely rounded lobules, sometimes with a strong tooth in one or both sides; apices variously dissected, typically with 3-4 narrow lobes, triangular or finger-like, then one cell wide, but lobes may be lacking or fused in polygonal appendage or reduced into small rounded bump; hyaline margin lacking; central cells oblong to rectangular, thick-walled, with inconspicuous trigones. NOTES Bazzania subtilis can be recognized by: 1) relatively small size; 2) shoots complanate both when dry and moist; 3) leaves asymmetrically oblong lingulate, with variously dissected apices, from obliquely truncate and shortly 3-dentate to obtuse and shallowly denticulate; and 4) underleaves patent-spreading, the apices typically with four finger-like lobes, and additional ones on lateral margins. Bazzania subtilis shares many features with B. incrassata especially complanate habit, conspicuous subvitta, leaf and underleaf main shapes. For distinctive characters, see under the latter. Like B. incrassata, weak forms occur among B. subtilis specimens with less dissected leaf and underleaf apices. Mastigobryum pulchellum Steph. (Stephani 1908b) was synonymized with Bazzania subtilis by Grolle (1980). In a paper on New Caledonian liverworts, Paris (1910b) added Mastigobryum pulchellum Steph. in a list of liverworts collected by Mrs and Mr Le Rat. But the corresponding specimen was later named Mastigobryum leratii (see under Bazzania consociata). However, B. subtilis was also quoted by Paris in the same paper as Mastigobryum subtile (from Dogny and Panié, not seen) and was therefore known since that date in the country.