Lejeunea giulianettii (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 : 35

5. Lejeunea giulianettii (Steph.) G.E.Lee & Heinrichs , comb. nov., Fig. 5 .

Taxilejeunea giulianettii Stephani (1914: 502) .

Type : PAPUA NEW GUINEA. Wharton Range, Giulianetti 1897 (lectotype G 012048 ! here designated; isolectotype JE!) .

Plants dioicous?, 2.0–3.0 mm wide, irregularly and densely pinnate to bipinnately branched, branches erect-spreading to spreading, with three rather large basal collar lobes. Stem 0.20–0.25 mm in diameter, about 8 cells high in cross-section; epidermal cells 7, 40–60 μm wide, medullary cells 20–25, 10–30 μm wide. Leaves closely imbricate, recurved when dry, erect-spreading and recurved when moist. Leaf lobes 1.50–1.75 mm × 1.3–1.5 mm (when flattened), ovateorbicular; leaf apex broadly rounded, always recurved; leaf margin entire; the ventral margin forming an angle of 80°–90° with the keel when flattened; insertion 20–23 lobe cells long. Leaf cells rather uniform, usually rounded; apical cells 15–25 μm × 15–25 μm, median cells 25–40 μm × 25–40 μm, basal cells 40–75 μm × 25–40 μm; cell walls hyaline, with well-developed trigones and intermediate thickenings, 1–2 per cell, 0–1(2 in the basal cells) between two adjacent trigones. Cuticle roughened by minute papillae. Leaf lobules rarely reduced, 0.4–0.5 mm × 0.2–0.3 mm, to 1/3 the length of the lobe, at an angle of 30°–45° to the stem, ovate–triangular, inflated along the keel; apex obliquely truncate; keel straight to slightly curved; free margin flat; first tooth 40–50 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 40–50 μm × 25–40 μm. Underleaves 0.8–1.0 mm × 0.6–0.9 mm, 4 times wider than the stem, distant, ovate (slightly wider than long); covering 3/4 of the leaf lobules; bilobed, lobes to 1/2 of underleaf length, about 20 cells wide, triangular; sinus broad, obtuse, U-shaped; margin entire; two large basal underleaf cells differentiated; tips obtuse; base straight. Androecia, gynoecia, sporophyte and vegetative propagation not seen.

Distribution:— only known from Papua New Guinea.

Discussion:— The distinguishing characters of L. giulianettii are 1) the relatively large plants, about 2–3 mm wide, 2) the apices of leaf lobes strongly recurved when dry or moist, 3) the broadly rounded leaf apex, 4) the well-developed trigones and intermediate thickenings of leaf cells, 5) the presence of two intermediate thickenings in basal leaf cells between adjacent trigones, 6) the flat free margin of leaf lobules, 7) the absence of a large rectangular disc cell, and 8) the distantly arranged underleaves. This species is somewhat similar to L. lumbricoides ( Nees 1830: 40) Nees in Gottsche et al. (1845: 342) [also mentioned by Eifrig (1937)] and also may be confused with L. stephaniana Mizutani (1964: 143) . All three species have relatively large plants and strongly recurved leaves, however, L. giulianettii differs by having a flat free margin of leaf lobules, cuticle roughened by minute papillae, and the presence of two intermediate thickenings in basal leaf cells between adjacent trigones. Furthermore, the lobes of underleaves in L. lumbricoides are often connivent to overlapping and the leaf lobules in L. stephaniana are always fully incurved. Lejeunea giulianettii varies particularly in the size and shape of leaves, underleaves and lobules on main shoots and branches. Main shoot leaves (2–3 mm wide) are significantly larger than branch leaves (0.75–1.25 mm wide); the same holds for the underleaves. Besides, the leaf lobules are ovate-triangular on main shoots whereas mostly ovate-oblong on branch leaves, and the free margin of lobules on branch leaves is sometimes fully incurved. Variation is also observed in the base of underleaves, which may be cordate to straight on the same shoot.

Figures

FIGURE 5. Lejeunea giulianettii (Steph.) G.E.Lee & Heinrichs. A. Part of plant in ventral view. B–D. Leaves. E. Stem portion and leaf lobule (hyaline papilla shown by arrow). F. Perianth with bracts and bracteole. G. Median cells of leaf lobe. H. Basal cells of leaf lobe. I–K. Underleaves.All figures drawn from the lectotype, Giulianettii 1897 (G).