Riccia junghuhniana Nees & Lindenb., Syn. Hepat.

Riccia junghuhniana Nees & Lindenb., Syn. Hepat. 4: 609. 1846.

Type: — INDONESIA, Java, Junghuhn s.n. (holotype: STR).

Plants in mats, terrestrial. Thallus medium-sized, 1.5–2.8 mm wide, 5.4–8 mm long; repeatedly 1–2 x furcate; ultimate branches shortly to deeply divided, obovate to oblong, apex rounded or truncate; color of upper surface light green to yellowish-green; dorsal furrow distinct, along length of branches; sections of thallus lobes 0.7–1.0 mm high and 2.6–3.5 times as wide as tall; air chambers present, narrow; cilia absent; ventral scales mottled hyaline to maroon, present on ventral flanks; rhizoids smooth and pegged, hyaline, covering ventral surface of midrib of thallus.

Monoicous. Antheridia and archegonia in 1–2 rows along midline of the thallus, necks hyaline, not prominent. Sporangia numerous. Spores 64–85 μm in diameter; triangular-globular; light brown to dark brown; distal face reticulate forming 6–10 areolae across the diameter, with papillae at corners; proximal face with similar ornamentation, triradiate mark indistinct; spore wing 3–4 µm wide, crenulate.

Specimens examined: — CHINA. Zhejiang: Kaihua County, Qianjiangyuan National Park, Gutianshan Nature Reserve, along the road from Gutianshanzhuang to gate of Qianjiangyuan National Park, 29°14’33.50” N, 118°6’38.56” E, 306 m, on soil, Y. Bai et al. 20201101-34 (HSNU); Y. Bai et al. 20201101-41 (HSNU); Kaihua County, Kukeng Village, 29°18’50.86” N, 118°11’37.02” E, 434 m, on soil, Y. L. Xiang & W. Z. Huang 20210417-14 A (HSNU). INDONESIA. Ambon Island, Waiyame County, near Dusun Bandaria, Rumah-Tiga Village, 3°39.221’ S, 128°10.221’ E, 120 m, on soil, R.- L. Zhu et al. 20170520-15 (HSNU).

Distribution and habitat: —So far, Riccia junghuhniana has been known from Australia (Northern Territory), China (Zhejiang), and Indonesia (Ambon, Bali, Java). In China, it grows on moist and shady soil at a low altitude, from 306 m to 434 m.

Notes:—The important features of Riccia junghuhniana include the 1) monoicy; 2) thalli growing as patches, not in rosettes or hemi-rosettes (Fig. 3A–B); 3) with narrow air chambers in thallus (Fig. 3O–P); 4) thallus 2–2.5 mm wide, 2.6–3.5 times as broad as thick in transverse section (Fig. 3O–P); 5) spores 64–85 µm in diameter, with complete alveoli on the distal face, 6–10 areolae across the diameter, with papillate corners (Fig. 3E–F & K–N), and 6) spore wings 3–4 µm wide, crenulate (Fig. 3C–D). The morphological comparison among samples from China and Indonesia showed that there were no obvious differences in the characters mentioned above.