9. Fissidens crassinervis Sande Lac., Verh. Kon. Ned. Akad. Wetensch., Afd. Natuurk. 13:3. 1872.
Plants small, dark green when young, brownish or reddish-brown when old, gregareous. Female leafy stems simple, 4.1–9.0 mm long, 1.2–1.8 mm wide; axillary hyaline nodules not differentiated; cortical stem-cells small, thick-walled; central strand weakly differentiated. Leaves in 8–17 pairs, lax, not overlapping at middle to lower part of stems, densely arranged at upper part of stems; upper leaves larger than lower ones, lanceolate to narrowly lanceolate, 1.1–1.5 mm × 0.15–0.25 mm, narrowly acute at apex; dorsal laminae wedge-shaped at base; vaginant laminae 1/2 – 1/3 the leaf-length, upper portion very unequal, usually open to costa; costa strong, percurrent to shortly excurrent; laminae usually 1 cell thick, but rarely 2 cells thick near margin; margins entire to subentire; cells of apical laminae irregularly quadrate to hexagonal, distinctly thick-walled, lumen 10–13 µm long, smooth.
Dioicous; male plants rare, mixed with female plants, much smaller than the latter, usually with less than 10 pairs of laxly arranged leaves; antheridia terminal; archegonia terminal on female plants, 19–220 µm long; perichaetial leaves narrowly lanceolate to linear, cells of upper part of vaginant laminae longer than those of other stem leaves. Setae 1.0–1.8 mm long; capsules erect, symmetrical; urns 0.6 mm long; exothecial cells quadrate, thin-walled with distinctly thickened corners.
Type. Indonesia: Java, 13 V 1860, Kurz s.n. (lectotype L).
Chinese specimens examined: TAIWAN: Ping-tung Co., T.-Y. Chiang 11759, 11839 (NICH).
Habitat: on soil in broad-leaved forest; Distribution: China, Japan, Thailand, Malaysia, Singapore, Indonesia, and New Guinea.
The present species is closely related to Fissidens laxus (= F. pellucidus), but the leaf shapes, the inflorescences, and the nature of laminal cells will distinguish them.
Illustrations: Pl. 76, figs. 1–15.