Lethocolea naruto-toganensis Furuki

Gradstein, S. Robbert, Ilkiu-Borges, Anna Luiza, Cargill, D. Christine, Beckmann, Karen & Vanderpoorten, Alain, 2024, An integrative taxonomic study of the genus Lethocolea (Marchantiophyta: Acrobolbaceae), Plant Ecology and Evolution 157 (3), pp. 375-398 : 375-398

3. Lethocolea naruto-toganensis Furuki ( Furuki 2001: 306)

Type.

Japan – Honshu • Chiba Prefecture, Naruto-machi, Naruto-Togane swamp, on wet sandy soil; ca 5 m; 2 Dec. 1994; Furuki 11806; holotype: CBM not seen .

Illustration.

Furuki (2001: fig. 1).

Brief description (after Furuki 2001).

Plants paroicous, green to brownish-green, small, up to 1 cm long and 2 mm wide, with ventral stolons. Stems ventral surface green (?). Rhizoids purple-red, rarely hyaline. Leaves imbricate, ovate, 1.0– 1.5 mm long and wide. Leaf cells rather large, 50–75 × 30–50 µm in midleaf, thin-walled, without trigones; cuticle smooth; oil bodies colourless, oblong, 7.5–20 × 7.5–10 µm, minutely granular, with 1–3 pupils (“ eye spots ”). Androecia bracts similar to leaves, not bulging; antheridia one per bract, positioned near the dorsal edge of the bract, stalk biseriate. Gynoecia terminal, bracts slightly larger than vegetative leaves. Marsupia up to 3 mm long, 0.5–0.7 mm wide, surface hairy, archegonia near the bottom of the marsupium. Sporophytes not observed. Gemmae positioned on the base of dorsal leaf margin near the stem apex, large, 15–20 cells across (0.3–0.5 mm), with a short, 1 - celled stalk, biconvex, margin 1–2 - stratose, crenulate, made of swollen cells, wing absent. Gemmalings originating from the margins of the gemmae.

Distribution.

Only known from the type locality in Japan (Central Honshu).

Habitat.

According to Furuki (2001), the plants grow on sandy lowlands along a river surrounded by rice fields and the soils are wet during the agricultural season but dry up during winter. As a consequence, the species dries up and disappears during the winter period. The habitat of the species is unusual and the only one of its kind remaining in Japan, other similar sites having been destroyed by land development. The locality is therefore preserved as a nature reserve by the Japanese government.

Notes.

Lethocolea naruto-toganensis is the only paroicous species in the genus; the type has not been seen and the description is based on Furuki (2001). In addition to its sexuality, the species stands out by having colourless oil bodies with 1–3 pupils (“ eye spots ”), purple-red rhizoids, relatively short marsupia, up to 3 mm long, and large, wingless gemmae, which originate from the bases of dorsal leaf margins, possessing a 1 - celled stalk and germinating at the gemma margins. Because of its smooth cuticle and large wingless gemmae, L. naruto-toganensis resembles L. pansa , but the latter species is dioicous and has hyaline rhizoids, greyish-brown oil bodies and much longer marsupia, up to 10 mm long. Moreover, the gemmalings of L. pansa originate from the centre of the gemmae. The possible presence of a gemma stalk, observed in L. naruto-toganensis ( Furuki 2001) , deserves study in L. javanica and L. pansa .