Lejeunea timokoponenii G.E. Lee & X.L. He

Lee, Gaik Ee & He, Xiaolan, 2024, A new species of Lejeunea (Lejeuneaceae) from Papua New Guinea, Phytotaxa 650 (2), pp. 194-198 : 195-197

Lejeunea timokoponenii G.E. Lee & X.L. He , sp. nov., Fig. 1

Type:— PAPUA NEW GUINEA. West Sepik Prov.: Frieda River prospecting area of Frieda Copper Co. Frieda R. Base Camp at Horse Creek , open gardens and lawns, 400 m alt., 4°42’S, 141°47’E, 1 August 1981, Timo Koponen 34857a (holotype H [c.per.]).

Plants dioicous (only gynoecium seen), 0.8–1.2 mm wide, irregularly and loosely branched, seldom bipinnately branched, branches spreading, with three small basal collar lobes. Stem ca. 0.1 mm in diameter, about 6 cells wide in cross-section; epidermal cells 7, 28–40 µm wide, medullary cells 13–15, 6–20 µm wide, ventral merophyte 2 cells wide. Leaf lobes 0.5–0.6 mm × 0.40–0.55 mm (when flattened), imbricate, ovate; leaf apex broadly rounded, with wavy margin curled upwards; leaf margin crenulate; the ventral margin forming an angle of 800 – 900 with the keel when flattened; insertion on dorsal side 10–12 lobe cells long. Leaf cells isodiametric; apical cells 16–20 × 15–20 µm, median cells 20–30 × 16–20 µm, basal cells 33–43 × 20–26 µm; cell walls hyaline, with well-developed trigones and frequently with intermediate thickenings, 1–2 per cell, 0–1 between 2 adjacent trigones. Cuticle smooth to weakly papillose. Oil bodies not seen. Leaf lobules seldom reduced (i.e. differing from its typical form, see Fig. 2 F, G in Lee et al. 2022 under Lejeunea malaysiana ), 0.25–0.35 × 0.15–0.20 mm, to 1/2–2/5 the length of the lobe, at an angle of 700 – 900 to the stem, ovate-triangular, inflated along the keel; apex obliquely truncate; keel curved; free margin incurved fully and abruptly flattened towards the apex; first tooth 25–28 µm long, oblong, apex obtuse; margin between tooth and sinus 3 cells long, large rectangular disc cell present (indicated by “*” in Fig. 1M or refer to Lee 2020 for further details), 40–45 µm long; hyaline papilla at the proximal side of the first tooth. Underleaves 0.3–0.4 × 0.6–0.7 mm, to 6–7 times wider than the stem, imbricate to approximate, reniform; fully covering the leaf lobules; bilobed, lobes to 1/3–1/4 of underleaf length, about 6–8 cells wide, triangular; sinus broad, obtuse, U-shaped; tips acute to obtuse; underleaf margin slightly crenulate; two large basal underleaf cells differentiated; base margin straight, insertion line curved. Androecia not seen. Gynoecia on short lateral branches, female bracts loosely arranged, with one innovation, with 1–2 gynoecia in a lateral position. Female bracts larger than the leaf, erect-spreading when moist, slightly enveloping the perianth. Lobes ca. 1.0 × 0.40–0.55 mm, obovate, apex broadly to narrowly rounded, margin crenulate. Lobules 0.4–0.5 × 0.1–0.2 mm, rarely reduced, 1/3 the width and 1/2–2/3 the length of the lobe, oblong, apex obtuse, keels straight, smooth, 0.4–0.5 mm long. Female bracteoles 0.7–0.8 × 0.45–0.60 mm, 3/4 of the perianth length, ovate with tips acute, lobes to 1/8 of female bracteole length, distant, sinus narrow, acute, margin crenulate. Perianths 0.7–1.2 × 0.4–0.5 mm, emergent to 1/7 of the perianth length, oblong, with 5 keels, margin of the keels sometimes lobed, undulate, cells of the perianth at the keels irregularly bulging on surface; beak 5–6 cells long; stalklike elongation lacking. Sporophyte and vegetative propagules not seen.

Additional specimens examined: West Sepik Prov.: Frieda River prospecting area of Frieda Copper Co. Frieda R. Base Camp at Horse Creek, open gardens and lawns, 400 m alt., 4°42’S, 141°47’E, 1 August 1981, on a bush, Timo Koponen 34826 (paratype H [c.per.]), ibid., Timo Koponen 34824 (paratype H), ibid., on cliff, Timo Koponen 34841 (paratype H), ibid., on soil, Timo Koponen 34818 A (paratype H).

Distribution and habitat: Only known from PNG, growing in an open, dry slope on a bush or soil at an elevation of 400 m.

Etymology: The species is named in honour of Professor Timo Koponen, a prominent bryologist, who collected the type specimens in West Sepik Province, PNG.

Discussion: The distinguishing characteristics of Lejeunea timokoponenii are: 1) the leaf margins curled upwards (particularly at the apex) including the female bracts, 2) the large, reniform underleaves 6–7 times wider than the stem, 3) the leaf cells with well-developed trigones and frequently with conspicuous intermediate thickenings, 4) the fully incurved free margins of the lobules, 5) the large disc cell below the first tooth of the leaf lobules, 6) the perianths with undulate keels and a 5–6 cells long beak. In its undulate-keeled perianth, leaf cells and outline of leaf lobules, L. timokoponenii resembles the previously documented Malesian species, L. dipterota ( Eifrig 1937: 96) Lee in Lee & Gradstein (2013: 61) (recently recorded in PNG fide Maul et al. 2023, Ellis et al. 2024). However, L. dipterota differs in the perianth character by having perianth keels with 2 wings and a beak that is only 2–3 cells long. On the other hand, the perianth of L. timokopenenii lacks wings and has a long beak, which is 5–6 cells long. Furthermore, L. timokoponenii is also distinguished by its distinct wavy leaf margins and large, reniform underleaves. This characteristic of large, reniform underleaves covering the leaf lobules is also observed in several species of Lejeunea , such as L. heinarii Lee & Pócs in Lee et al. (2020: 493), L. mimula Hürlimann (1993: 12) , L. leratii ( Stephani 1914: 562) Mizutani (1970: 243) , and L. sordida ( Nees 1830: 41) Montagne (1840: 335) . However, none of these species exhibits the wavy or upward curling of leaf margins present in L. timokoponenii .

Figures

FIGURE 1. Lejeunea timokoponenii G.E. Lee & X.L. He. A. Part of plant in ventral view. B,C. Leaves. D,E. Underleaves. F. Upper portion of perianth. G. Perianth. H. Median cells of leaf. I. Stem portion and leaf lobules. J. Cross-section of stem. K,L. Female bracts. M. Upper part of leaf lobules when flattened (hyaline papillae and disc cell shown in gray and asterisk, “*”, respectively). N. Perianth with bracts and bracteole. All from the holotype, Timo Koponen 34857a (H). Illustrations drawn by G.E. Lee.