15. Fissidens flabellulus Thwait. & Mitt., J. Linn. Soc., Bot. 13:324. 1873.
Plants small to very small. Leafy stems 0.7–1.4 mm long, 0.6.–1.2 mm wide, simple to rarely branched, densely foliated; central strand lacking; axillary hyaline nodules more or less differentiated. Leaves in 2-7 pairs; upper leaves lanceolate to narrowly lanceolate, 0.7–1.2 mm × 0.1-0.3 mm, acute to narrowly acute at apex, wedge-shaped at base of dorsal laminae; vaginant laminae about 1/2 – 1/3 the leaf length; costa stout, percurrent to shortly excurrent, often dividing laminae unequally, dorsal side often wider than ventral side at middle of leaves; margins of vaginant laminae more or less distinctly serrate by projecting laminal cells; cells of apical laminae quadrate to hexagonal, 10–17(–19) µm long, slightly mammillose to almost smooth, walls clear, moderately thick-walled; cells at upper part of vaginant laminae similar to those of apical laminae. Rhizoautoicous or autoicous; male inflorescence often terminal on stems; archegonia terminal on stems, 160–170 µm long. Setae 1.6–3.5 mm long; capsules ovoid to shortly cylindrical, erect and symmetrical; urns 0.3–0.5 mm long; exothecial cells quadrate, thin-walled with weakly thickened corners; opercula long conical to rostrate, 0.3–0.4 mm long. Calyptrae campanulate, ca 0.4 mm long, smooth. Spores 11–14 µm in diameter, almost smooth.
Type. Sri Lanka (Ins. Ceylon), Thwaites 142 (isotype? NY).
Chinese specimen examined: YUNNAN: Meng-la Co., Mengxing River at Kilometer marker 71 along Menglun-Menxing road, Magill, Redfearn & Crosby 7790 (MO, NICH).
Habitat: on soil or base of trees; Distribution: China, Japan (Bonin), and Sri Lanka.
This species is closely related to Fissidens serratus. However, it is easily separated from the latter by having larger (10–19 µm) and smooth to almost smooth laminal cells.
Illustrations: Pl. 78, figs. 17–37.