Pycnolejeunea contigua (Nees) Grolle

Promma, Chatchaba & Chantanaorrapint, Sahut, 2025, The genus Pycnolejeunea (Lejeuneaceae, Marchantiophyta) in Thailand, with the description of Pycnolejeunea zhuiana, PhytoKeys 259, pp. 145-160 : 145-160

1. Pycnolejeunea contigua (Nees) Grolle , J. Hattori Bot. Lab. 45: 179. 1979.

Figs 1 , 2

≡ Jungermannia contigua Nees in Martius, Fl. Brasil. enum. plant. 1 (2): 360. 1833. Type: Brazil. Pará: ad corticem arborum, C. F. Martius s. n. (isotype: G [ G 00128260]).

= Pycnolejeunea bancana Steph. , Hedwigia 35: 124. 1896. Type: Indonesia. Insula Banca, 1883, J. E. Teysmann s. n. (lectotype: G [ G 00281813], designated by He (1999)).

= Pycnolejeunea papulosa Steph. , Hedwigia 35: 125. 1896. Type: Brazil. Pará: Caripi, R. Spruce s. n. (lectotype: G [ G 00128263], designated by Grolle (1979); isolectotypes: G [ G 00128261, G 00128262], JE, M, W).

= Pycnolejeunea densiuscula Spruce ex Steph. , Sp. Hepat. 5: 613. 1914. Type: Brazil. Pará: Silva Amazonica, Santarém, Dec 1849, R. Spruce s. n. (lectotype: G [ G 00128259] designated by Grolle (1979); isotype: G [ G 00128258], JE, M).

= Pycnolejeunea ocellata Steph. , Sp. Hepat. 5: 614. 1914. Type: Cuba. C. Wright s. n. (lectotype: G [ G 00128226], designated by He (1999); isolectotype: JE [ JE 04002710]).

Description.

Plants whitish-green or light green when fresh, yellowish-brown or light brown in dry condition; shoots 0.9–1.5 mm wide, usually scarcely and irregularly branched; branches Lejeunea - type. Stems 100–130 µm diameter, in transverse section with 9 (– 10) epidermal cells, surrounding 14–18 medullary cells, epidermal cells larger than medullary cells; cell walls pale brown or yellowish-brown, thick-walled, with triangular to bulging trigones, wall between trigones with thin to rather thick continuous thickenings; ventral merophyte 2 cells wide. Rhizoids at base of underleaves, few, tufted, usually hyaline, rhizoid disc not seen. Leaves closely imbricate, when moist, wide-spreading. Leaf lobes ovate to oblong-ovate, rarely falcate-ovate, 725–827 µm long, 544–617 µm wide, dorsal margin arched, ventral margin arched, margin entire to slightly crenulate with projecting cells, apex rounded, incurved. Lobe cells convex or weakly mammillose on dorsal side, thin-walled, with small to large triangular trigones, intermediate thickenings absent or occasionally seen in the basal cells; marginal cells rectangular or quadrate, 16.5–20.8 × 15.0–23.7 µm; median cells hexagonal to rounded, 22.5–37.0 × 21.5–38.5 µm, basal cells hexagonal to rectangular, 22.0–45.8 × 20.0–30.0 µm; ocelli rectangular to long hexagonal, 47–65 × 25–40 µm, (0 –) 1–5 per leaf lobe, basal, aggregated or isolated; oil bodies 3–5 per cell, long ellipsoidal to ovoid-cylindrical, 10.4–19.8 × 3.7–5.1 µm, Calypogeia - type, coarsely granular. Lobules small, ovate, 152–182 µm long, 120–135 µm wide, inflated, 0.2–0.3 of lobe length, free margin slightly involute, formed by 5–7 elongated cells, apex semicircular, apical tooth short, 1 - celled, obtuse, keel arched or nearly straight, lobule cells smooth or slightly convex. Underleaves imbricate, rarely contiguous, suborbicular to reniform, 287–330 µm long, 416–458 µm wide, wider than long, 3–5 of stem width, bifid to 1 / 2 of its length, lobes triangular with acute to obtuse apex, margin nearly entire or bluntly toothed at side, sinus V-shaped, bases rounded to cuneate, insertion line arched. Asexual reproduction by unmodified caducous leaves, lobules remain attached to the stem; or modified caducous leaves arising from upright flagelliform shoots on branch apices, smaller than ordinary leaves, margins usually with 1 - celled rhizoids. Sexuality autoicous. Androecia, gynoecia and sporophytes not seen.

Distribution, habitat and ecology.

Pantropical ( He 1999; Bastos et al. 2020). In Thailand, Pycnolejeunea contigua was found on tree trunks and branches in forest gaps, along forest margins or open habitats in coastal sand dune and tropical lowland forests, ranging from sea level to 480 m above sea level.

Taxonomic notes.

Pycnolejeunea contigua is a widely distributed species distinguished by its pale to glossy brownish plants, 1–5 basal ocelli per leaf lobe (aggregated or isolated) and large broadly ovate to reniform underleaves that almost completely cover the lobules. Asexual reproduction occurs via unmodified caducous leaves with lobules remaining attached to the stem and usually by modified caducous leaves arising from flagelliform shoots.

In Thailand, P. contigua is most similar to P. grandiocellata , sharing several vegetative features such as ovate to oblong leaf lobes, 2 - celled wide ventral merophytes and smooth to slightly convex lobule cells. However, P. contigua differs in having 1–5 ocelli which are basal in position, whereas P. grandiocellata exhibits more ocelli (4–15) suprabasal ocelli commonly aggregated from the base to the ventral half of the lobe. Additionally, the presence of modified caducous leaves (flagelliform shoots) in P. contigua further distinguishes it from P. grandiocellata , which produces only unmodified caducous leaves.

Specimens examined.

Thailand. Phang Nga: Hat Thai Mueang - Khao Lampi National Park , 8°29.1523'N, 98°13.6872'E, 18 m elev., 10 Oct 2015, O. Suwanmala 111, 119 A ( PSU) ; 8°29.011'N, 98°13.7605'E, 13 m elev., 30 Jan 2016, O. Suwanmala 186 ( PSU) ; Krabi: Hat Noppharat Thara - Mu Ko Phi Phi National Park, Khao Ngon Nak Mountain , 8°5.2767'N, 98°46.47'E, 480 m elev., 24 Mar 2018, A. Senayai 75 a, 126 b ( BKF, PSU) ; 12 Oct 2018, A. Senayai 212 ( BKF, PSU) ; 8°5.2767'N, 98°46.47'E, 480 m elev., 15 Feb 2025; C. Promma & K. Chanakarn 20250215-19, 20250215-28 B ( PSU) ; Yala: Betong, Ban Piyamit 2 , 14 Jun 2013, S. Chantanaorrapint & C. Promma 2515 ( PSU) .

Figures

Figure 1. Pycnolejeunea contigua (Nees) Grolle. A. Portion of sterile plant, ventral view; B. Portion of sterile plant with flagelliform shoot, ventral view; C. Transverse section of stem; D – F. Lateral leaves; G. Cells from basal and near middle portion of leaf, dorsal view; H. Cells from apical leaf margin; I. Leaf lobule; J – M. Underleaves. Drawn by C. Promma; based on C. Promma & K. Chanakarn 20250215-28 B (PSU).

Figure 2. Pycnolejeunea contigua (Nees) Grolle. A. Portion of sterile plant, ventral view; B. Portion of sterile plant with flagelliform shoot, ventral view; C. Flagelliform shoot; D. Portion of sterile plant, showing underleaves; E. Underleaf; F. Lateral leaf; G. Leaf lobule; H. Transverse section of leaf; I. Transverse section of stem; J – M. Cells from basal portion of leaf, showing ocelli. Photographed by C. Promma; based on C. Promma & K. Chanakarn 20250215-28 B (PSU).