Lejeunea compressiuscula (Steph.) G.E.Lee & Heinrichs, 2018

Lee, Gaik Ee, Bechteler, Julia & Heinrichs, Jochen, 2018, A revision of unrevised taxon names in the former genus Taxilejeunea (Marchantiophyta: Lejeuneaceae) from Asia, Phytotaxa 358 (1), pp. 26-48 : 28

1. Lejeunea compressiuscula (Steph.) G.E.Lee & Heinrichs , comb. nov., Fig. 1 .

Taxilejeunea compressiuscula Stephani (1914: 501) .

Type: INDONESIA. Java: Hampe s.n. (lectotype G 16251! [scanty, 3 shoots, c. per.], here designated). Lejeunea compressiuscula Lindb. ex Stephani (1914: 501) , nom. nud.

Plants autoicous, 1.5–2.0 mm wide, irregularly and slightly to densely branched, sometimes bipinnately branched, branches spreading, with three small basal collar lobes. Stem 0.10–0.15 mm in diameter, about 6 cells high in cross-section; epidermal cells 7, 25–45 μm wide, medullary cells 12–13, 13–20 μm wide. Leaves contiguous to slightly imbricate, plane when dry, erect-spreading to spreading and plane when moist. Leaf lobes 0.8–1.0 mm × 0.5–0.8 mm (when flattened), ovate-oblong; leaf apex broadly rounded, flat; leaf margin entire; the ventral margin forming an angle of 180° with the keel when flattened; insertion 10–13 lobe cells long. Leaf cells rather uniform, quadrate to hexagonal, rarely round; apical cells 20–25 μm × 13–18 μm, median cells 25–38 μm × 20–25 μm, basal cells 38–50 μm × 25–38 μm; cell walls hyaline, with well-developed trigones and infrequently with intermediate thickenings, 1–2 (3) per cell, 0–1 between 2 adjacent trigones. Cuticle roughened by numerous minute papillae. Leaf lobules frequently reduced, 0.15–0.20 mm × 0.10–0.13 mm, to 1/4–1/5 the length of the lobe, at an angle of 80°–90° to the stem, ovate to oblong, inflated along the keel; apex obliquely truncate; keel somewhat straight, rarely curved; free margin flat; first tooth 25–38 μm long, oblong, somewhat erect, apex obtuse; margin between tooth and sinus 3 cells long; large rectangular disc cell undifferentiated, cell below the first tooth 30–38 μm × 20–25 μm. Underleaves 0.2–0.3 mm × 0.35–0.40 mm, to 3 times wider than the stem, distant, suborbicular to wider than long; covering 1/3–1/2 of the leaf lobules; bilobed, lobes to 1/2–2/3 of underleaf length, about 8–10 cells wide, triangular; sinus narrow to broad, U-shaped to V-shaped; tips acute to obtuse; underleaf margin entire; two large basal underleaf cells differentiated; base ± cuneate, insertion line curved. Androecia 0.30–0.45 mm × 0.2–0.3 mm with bracts, on the main shoots or lateral branches. Male bracts in 2–4 pairs, entire without wing, apex obtuse, keels inflated. Male bracteole 1, smaller than underleaf, margin entire. Antheridia not seen. Gynoecia on short or long lateral branches, female bracts loosely arranged, with one innovation, with 1–2 gynoecia in a lateral position. Female bracts smaller than the leaf, erect-spreading when moist, not enveloping the perianth. Lobes 0.5–0.6 mm × 0.30–0.35 wide, obovate to somewhat oblong, apex obtuse, margin entire. Lobules 0.20–0.25 mm × 0.05–0.10 mm, rarely reduced, 1/4 the width and 1/2 the length of the lobe, oblong, apex obtuse, keels straight, smooth, 0.18–0.20 mm long. Female bracteoles 0.3–0.4 mm × 0.15–0.20 mm, 1/2 of the perianth length, ovate to oblong with tips acute, lobes to 1/3–1/2 of female bracteole length, distant, sinus narrow, acute, margin entire. Perianths 0.45–0.70 mm × 0.15–0.40 mm, emergent to 1/2–2/3 of the perianth length, oblong, with 5 keels; beak 2–3 cells long; cells of the perianth at the keels entire, sometimes slightly mamillose; stalk-like elongation lacking. Sporophyte and vegetative propagation not seen.

Further specimen examined:— SRI LANKA. NUWARA ELIYA: Haputale, abbaye bénédictine, M. Onraedt 77.L.3885 (JE).

Distribution:— Sri Lanka, Indonesia (Java).

Discussion:— The distinguishing characters of L. compressiuscula include 1) ovate-oblong leaves with broadly rounded apices, 2) the ventral margin forming an angle of 180° with the keel when flattened, 3) leaf cells with well-developed trigones and infrequently intermediate thickenings, 4) relatively small and frequently reduced leaf lobules, 5) the flat free margin of leaf lobules, 6) distant and suborbicular to wider than long underleaves, and 7) oblong perianths. Lejeunea compressiuscula closely resembles L. micholitzii Mizutani (1970: 236) in most of the important characters, however the former is distinguished from the latter by the autoicous plant, the ventral margin which forms an angle of 180° with the keel when flattened, the rough cuticle, the flat free margin of leaf lobules, and the oblong perianths. Thus far, L. compressiuscula is only known from the type specimen in Java and two collections in Sri Lanka ( Onraedt 1981: 214). Perhaps this species has been confused with L. micholitzii in the past, e.g., all the specimens of L. compressiuscula determined by Eifrig in JE are indeed L. micholitzii .

Figures

FIGURE 1. Lejeunea compressiuscula (Steph.) G.E.Lee & Heinrichs. A. Part of plant in ventral view. B–C. Leaves. D. Cross-section of stem. E. Perianth with bracts and bracteole in ventral view. F–H. Underleaves. I. Perianth with bracts and bracteole in dorsal view. J. Median cells of leaf lobe. K–L. Stem portion and leaf lobule. All figures drawn from M.Onraedt 77.L.3885 (JE).