Lethocolea drummondii Mitt., nom. illeg. (= L. pansa (Taylor) G.A.M.Scott & K.G.Beckm.).

Plants dioicous, rarely paroicous (L. naruto-toganensis), prostrate, pale green to yellowish-green to olive-green to brownish, sometimes reddish or purplish, little-branched, branching ventral-intercalary or (rarely) lateral-intercalary, ventral branches stoloniform. Stems rather fleshy, usually fragile and made up of thin-walled cells, sometimes rigid and with slightly thickened epidermal walls, epidermis cells similar in size to medullary cells, rarely slightly smaller, ventral region of stem sometimes with fungal hyphae inside the cells. Rhizoids scattered to slightly fascicled, hyaline to light brown to pink, rarely purplish (L. naruto-toganensis), sometimes with fungal hyphae. Leaves succubous, alternate, imbricate, lamina flat to convex, or concave with convex margins, undivided, suborbicular to ovate to ovate-oblong to lingulate, insertion line reaching dorsal midline of stem, apex rounded to truncate to emarginate, margins entire, sometimes with a border of thick-walled cells, dorsal leaf base not or shortly decurrent, ventral leaf base not decurrent, lower ventral half of the leaf lamina with an area of enlarged, hyaline cells with little or no chlorophyll. Leaf cells isodiametric to elongate, fully thin-walled or with very small to medium-sized trigones, trigones usually hyaline, rarely reddish, cuticle coarsely papillose or smooth; oil bodies large, 1–3 per cell, usually ellipsoid, dark brown to greyish-brown (exceptionally colourless), sometimes persistent in dried material. Underleaves absent. Androecia terminal or intercalary on main shoots, bracts saccate (not saccate in L. naruto-toganensis), antheridia 1(–6) per bract, antheridial stalk short, up to 7 cells long, irregularly biseriate. Gynoecia terminal on main shoots, female bracts in 2–4 pairs, bracts slightly larger than vegetative leaves (except for the inner ones), standing upwards or spreading outwards; perianth absent; archegonia ca 20–30 per gynoecium. Marsupia pendent, shortly to elongate cylindrical, up to 3–10(–20) mm long, green and with smooth surface when young, brown and with usually hairy surface when mature, marsupial canal narrow, lined by few or numerous large, elongate, papilliform, mucilaginous cells; archegonia, calyptra and developing sporophyte carried to the base of the marsupium, archegonia with a short neck. Setae whitish, up to 1.2 cm long after elongation, massive, made up of ca 70 rows of cells (Fig. 9D), with distinct trigones. Capsules cylindrical, scarcely wider than the seta, tip acute to apiculate (Fig. 9C), capsule dehiscence complete or incomplete, splitting to the base into 4 or in only 2–3 valves with two adjacent valves remaining partially connate, capsule wall 2–4-stratose (Fig. 9F), cell walls of the outer layer yellowish to reddish-brown, with small, orange to reddish-brown nodular thickenings evenly spaced along the outer longitudinal wall and turning into conspicuous thickening bands on radial walls, cell walls of the inner layers hyaline, without thickenings (seen in L. congesta only); elaters with 1–2 spirals (seen in L. congesta only), narrowly fusiform, 130–200 × ca 10 µm, surface finely punctate; spores isodiametrical, ca 25 µm in diameter, yellowish to brown, surface finely papillose. Asexual reproduction (subgen. Lethocolea) via large, disciform (sometimes angular-shaped) gemmae produced near the shoot apex on the dorsal stem surface or on the bases of the dorsal leaf margins, gemmae green to light brown, 1–5 mm in diameter, 4–20 cells across, biconvex, 5–6 cells thick in the middle and 1–2 cells thick at the margin, sometimes with a 1-celled stalk, with or without transparent, unistratose wing; gemmalings sprouting from the centre or the margin of the gemmae.

Widely distributed in Mediterranean and temperate regions of the Southern Hemisphere and in tropical mountains, extending northwards to Mexico, India, and Japan.

On sandy, loamy, or peaty soils subject to desiccation, in shaded and exposed sites, along trails, on earth walls and on soil over rock, sometimes in swampy, wet habitats, or floating on water, becoming deeply reddish-maroon. The plants sometimes grow partly buried in the substrate and may become brownish, somewhat purplish or carmine when growing in exposed sites.

Lethocolea is readily recognized by: 1) creeping, little-branched leafy shoots with rather fragile stems made up of thin-walled cells, without or with one (or more) ventral stolons; 2) rhizoids scattered, hyaline to light brown to pink (exceptionally purplish); 3) leaves succubous, insertion line reaching dorsal midline of stem, alternate, imbricate, undivided, suborbicular to ovate-oblong to lingulate, with a broadly rounded apex, entire margins and an area of enlarged hyaline cells in the lower ventral half of the leaf; 4) leaf cells with or without trigones, trigones hyaline, cuticle coarsely papillose or smooth, oil bodies 1–3 per cell, large, finely granular, greyish-brown to dark brown; 5) underleaves absent; 6) gametoecia on main shoots; 7) sporophyte enclosed by a pendent marsupium at the shoot apex (perianth absent); 8) calyptra present, free, carried down the marsupial canal to the foot of the marsupium together with the unfertilized archegonia; 9) capsule cylindrical, tip acute to apiculate; 10) asexual reproduction by multicellular, disciform gemmae (in subgen. Lethocolea).

By its undivided succubous leaves, lack of underleaves, and rather large, finely granular oil bodies, one or two per cell, Lethocolea has been confused with Jackiella (Jackiellaceae), Odontoschisma (Cephaloziaceae), and Solenostoma (Solenostomataceae). The latter three genera are distinguished from Lethocolea by the absence of an area of enlarged-hyaline cells in the lower ventral half of the leaf and by the smooth or finely papillose cuticle covered by minute papillae much smaller than in Lethocolea. Jackiella and Odontoschisma, moreover, have dorsal leaf insertions usually not reaching the dorsal midline of stem, gametangia on short ventral branches, and asexual reproduction by small, 1–2-celled gemmae. The sporophyte is enclosed by a perianth in Odontoschisma and Solenostoma, and by a marsupium in Jackiella.

Based on the results of the morphological and molecular study, four Lethocolea species are recognized in two subgenera, subgen. Lethocolea and subgen. Symphyomitra. The two subgenera are distinguished by the presence or absence of disciform gemmae, the length and shape of the marsupium, and the incidence of papilliform cells lining the marsupial canal (Grolle 1972). The two groups are fully supported in the molecular analysis (Fig. 2). Schuster (2021) treated the two subgenera as sections, but in view of the strong molecular support for the two groups we do not accept Schuster’s classification.

Sporophytes are rare in Lethocolea; the above description is based on two sporophytic collections of L. congesta, with additions from Spruce (1885) and Schuster (2021). The seta of Lethocolea is massive and the capsule is cylindrical with an apiculate tip (Fig. 9C, D), like in other members of Acrobolbaceae (Schuster 2021). The capsule of L. congesta is unusual, however, in opening to the base into 2–4 valves (with two adjacent valves sometimes remaining partially connate) and in having a thin, mostly 2-stratose wall, with limited 3–4-stratose areas (Fig. 9F) and no thickenings on the walls of the inner cell layers (Fig. 9G, I) (capsule opening to the base into 4 valves, wall 4–10-stratose and with thickenings in all cell layers in other Acrobolbaceae). Moreover, the elaters of L. congesta possess 1–2 spirals (Fig. 9B) (elaters bispiral in Acrobolbaceae). Data on capsule wall thickenings and elaters are still lacking for the other species of Lethocolea. The sporophyte of Lethocolea clearly needs more study.

Stems ventral surface green or dark purplish-reddish pigmented; stolons present or absent. Leaf cells with smooth or densely papillose cuticle; oil bodies one per cell (Fig. 3E, F), ellipsoid, ca 10–25 µm long, greyish-brown, rarely colourless (L. naruto-toganensis), finely papillose, sometimes with 1–3 pupils or “eye spots” (= larger and lighter-coloured granules). Antheridia one per bract. Marsupia usually long and slender, narrowly cylindrical, (3–)8–15 mm long, when mature with swollen tip (Fig. 6B), wall 5–6 cells thick, marsupial canal lined by numerous elongate, papilliform cells that nearly fill the canal. Capsules splitting to the base into 4 valves. Asexual reproduction by disciform gemmae produced near the shoot apex on the dorsal surface of the stem or on the base of dorsal leaf margins (L. naruto-toganensis), gemmae 4–20 cells across, 0.1–0.5 mm in diameter, biconvex, becoming thinner to the margin and sometimes with a 1–2 cell wide unistratose, transparent wing.

Figure 6. 

Lethocolea pansa. A, G. Female shoot with immature marsupium. B. Female shoot with mature marsupium. C. Cross section of stem. D. Cells at leaf apex. E. Gemma. F. Portion of shoot with gemmae, dorsal view. H, J–L. Leaves. I. Sterile shoot. M. Cells at ventral leaf base. N. Midleaf cells. O. Cells at dorsal leaf base. A, C–E, G–I, M–O from Esterhuysen 27343; B, L from Hedderson 152686; F, J–K from Arts 129/11. Drawn by Anna Luiza Ilkiu-Borges.

Three species in Australasia, Java, India, Japan, and South Africa.

Australia – West Australia • Swan River; on clay; s.d.; Drummond s.n.; lectotype (designated here): FH [FH01122546]; isolectotype: BM [BM013763002].

Plants dioicous, 1–2 cm long, 1–3 mm wide, creeping, flaccid, glossy green to purplish when fresh, usually brownish in herbarium, with or without a short ventral stolon near the base, lateral branches scarce, innovations not observed. Stems ca 0.2–0.4 mm in diameter, rather fleshy and fragile, made up of large, thin-walled cells, upper surface green to brownish-green, ventral surface usually dark purplish-reddish. Rhizoids scattered, hyaline. Leaves present throughout the stem, succubous, imbricate, obliquely to widely spreading, somewhat asymmetrically ovate to ovate-oblong, 0.9–1.6 × 0.6–1.2 mm, ca 1.5× longer than wide, flat or slightly concave, usually unpigmented, occasionally with some brownish-purple pigmentation in older portions of the stem, apex broadly rounded, dorsal and ventral bases not decurrent. Leaf cells thin-walled, without or with very small trigones, less than 3 µm in diameter, sides of trigones concave (not bulging outwards), subrectangular, in the ventral and basal part of the leaf much larger than in the dorsal and apical part, dorsal cells 30–50 × 20–35 µm, ventral cells 40–100 × 30–50 µm, towards the leaf base over 100 µm long; margin cells slightly smaller, subquadrate, ca 25–30 µm; cuticle smooth; oil bodies (degenerated in herbarium material) always one per cell, ca 10–20 µm long, greyish-brown. Androecia terminal, bracts in 3–4 pairs, base saccate; antheridia one per bract, ovoid, with a short, biseriate stalk. Gynoecia bracts in 3–5 pairs, slightly larger than vegetative leaves (except for the smaller inner bracts at the mouth of the marsupium), spreading outwards, flat, dorsal margin somewhat undulate. Marsupia linear, green to greenish-brown, with almost smooth surface, up to 10 mm long, ca 0.5 mm in diameter, marsupial canal lined by numerous large, elongate, papilliform cells. Sporophytes not observed. Gemmae positioned on the dorsal stem surface or in leaf axils near the stem apex, dull green to light brown, orbicular to slightly longer than wide, 0.2–0.4 mm in largest diameter, 8–20 cells across, biconvex, 5–7 cells thick in the middle, 1–2 cells thick at the margin, cells subisodiametric, ca 25 µm in diameter, margin cells not or partially transparent only, not forming a distinct wing, outer wall convex but usually not protruding outwards (exceptionally one or two cells protruding outwards), margin of gemmae crenulate. Gemmalings common, much more slender than ordinary plants, originating from the centre of the gemmae and consisting a long, almost colourless, almost bare microphyllous shoot terminating in a few densely imbricate leaf pairs.

Australia, New Zealand, South Africa. The distribution of Lethocolea pansa in Australia and New Zealand needs further study as part of the published records from these countries (e.g. Engel and Glenny 2019; Schuster 2021), viz. plants with a papillose cuticle, distinct trigones, and winged gemmae, belong to L. javanica (see below). As shown here, published records of L. pansa from New Caledonia (Stephani 1922 as Gongylanthus leratae; Hürlimann 1974, 1985) belong to L. javanica as well.

On bare, moist soil along trails, on road cuts and in open, mesic woodlands and scrub, also on soil over sandstone rock and near water, ca 150–1000 m. Scott (1985) noted that Lethocolea pansa may have the widest ecological tolerance of any Australian liverwort, “growing in dry and hot at one extreme, but found as a floating aquatic at the other extreme, and all stages between”, but Scott and Beckmann (1987) found that records from very dry habitats belonged to Gongylanthus scariosus (Lehm.) Steph. Moreover, the present study shows that part of the published records of L. pansa from Australasia refer to L. javanica.

Australia – New South Wales • Kyeamba Travelling Stock Reserve South of Tarcutta; 356 m; c. gemm.; Purdie 8216A; CANB [CANB800536] • Weddin State Forst, 17 km SW of Grenfell; Curnow 1850; CANB [CANB8900876] • Lachlan Range State Forest, 15 km NW of Rankins Springs; c. gemm.; Curnow 3367; CANB [CANB9404944] • Goonoo State Forest, 5 km E of Mogriguy Forest Road, ca 23 km direct NNE of Dubbo; c. gemm.; Curnow 6567; CANB [CANB672034] • Goonoo State Forest, 3 Corners road, 1.5 km W of Dubbo – Mendooran road; c. gemm.; Curnow 6597A; CANB [CANB672077]. – Northern Territory • NE Arnhem Land, Gore, Rindarry Creek; Russell-Smith 4829; CBG [CBG8803914]. – Queensland • Silver Valley Road, 4.4 km by road SW of Herberton; c. gemm.; Curnow 6871; CANB [CANB898903]. – South Australia • Kangaroo Is., Western River Conservation Park, Waterfall Creek, 30 km ENE of Cape Borda; Streimann 54953; CBG [CBG9511339]. – Western Australia • Serpentine National Park, 2.5 km S of Jarrahdale; 150–200 m; Pócs 04143/M; EGR • Darling district, Perup Ecological Reserve; Cargill 665; CANB [CANB7590021] • Bullfinch Evanston Road, 69.3 km (by road) N of Bullfinch; Curnow WA118; CANB [CANB879890] • Karolin Rock, 20 km (by road) NW of Bullfinch; Curnow WA130; CANB [879902] • North Boundary Road, ca 3 km N of Kingston Road, ca 5 km E of Yornup; Cargill 1200WA; CANB [CANB900850] • ‘Grevillea Rock’, ca 25 km by road SE of Bridgetown, ca 1 km N towards Winnejup; Cargill 685GR; CANB [CANB759031].

South Africa – Western Cape Province • Kasteel Poort; Arnell 1031; BOL • Kasteel Poort; Arnell 1036; paratype of Symphyomitra tabularis; G • Constantia slopes; Arnell 323; BOL, JE (2 colls.) • Constantia slopes; Arnell 387; BOL • Constantia Nek; Arnell 316; BOL • Track from Constantia Nek to Table Mountain; 630 m; Arts 129/11; BR [BR5040313689887] • De Hoek, North foot of Zitzikanna Mts near Joubertina; ca 550 m; c. gyn.; Esterhuysen 27343; BOL • Riviersonderend Mts, Boesman’s Kloof, path below De Galg; ca 1000 m; Hedderson 15268b; BOL • Swellendam-Ashton area, W slopes of Langeberg, Sitruspoort farm; ca 600 m; c. gyn.; Hedderson 15301; BOL.

Lethocolea pansa is characterized by the glossy green to brown (occasionally purplish) plants with dark purplish-reddish ventral stem surfaces, hyaline rhizoids, very thin-walled leaf cells without or with very small trigones, smooth cuticles, a single greyish-brown oil body per cell, up to 10 mm long marsupia, and dull green to brownish gemmae, 8–20 cells across, with a crenulate margin and no wing. Lethocolea pansa has been confused with L. javanica, which had been included as a synonym in L. pansa by recent authors following Grolle (1965, as L. squamata). Lethocolea javanica differs from L. pansa in the dull green (shaded sites) to carmine-red (exposed sites) plant colour, leaf cells with distinct trigones and a densely papillose cuticle (to be studied carefully: in older herbarium material the papillae may be somewhat inconspicuous), and smaller, pale-green gemmae with a strongly crenate margin and 1–2 cell wide transparent wing (Figs 3–5). Scott and Beckmann (1987), moreover, found that gemmalings of L. pansa germinated from the centre of the gemmae, supporting the earlier findings of Goebel (1906) from plants he had identified as L. drummondii. In contrast, gemmae of L. javanica (identified as L. squamata) germinated from the margins. Due to the densely papillose cuticle and the well-developed trigones, L. javanica is a more dull-coloured plant than L. pansa, and more rigid. The detailed description and illustration of L. pansa in Engel and Glenny (2019) is a combination of L. javanica and L. pansa.

The leaves in Lethocolea pansa are ovate to ovate-oblong (1.0–1.7: 1), but in one collection from Serpentine National Park, Western Australia (Pócs 04143/M), they are ovate-orbicular to narrowly lingulate, becoming increasingly elongate towards the base of the shoots. As a result, the outline of these plants is more or less triangular.

Lethocolea pansa resembles L. naruto-toganensis from Japan in the smooth cuticle and the wingless gemmae; the latter species differs from L. pansa in having purplish rhizoids, green stem undersides, colourless oil bodies, and paroicous sex distribution. Moreover, the gemmalings of L. naruto-toganensis originate from the margins of the gemmae (Furuki 2001), while those of L. pansa originate from the centre.

Lethocolea pansa is newly recorded here from South Africa, where it was previously labelled as L. congesta or Symphyomitra tabularis (Arnell 1953). The latter species was described based on a mixture of L. congesta and L. pansa, and was placed in the synonymy of L. congesta by Arnell (1955, 1963). Lethocolea congesta clearly differs from L. pansa in the rather dull-coloured, green to yellowish-green to yellowish-brown plants with unpigmented stems (but leaves may occasionally be tinged purple), leaf cells with trigones, a densely papillose cuticle, and 1–3 dark brown oil bodies per cell (usually 2) (Figs 1, 3) The marsupia of L. congesta are significantly shorter than those of L. pansa, up to maximally 3 mm, and the marsupial canal is lined by few large, papilliform cells. Gemmae are absent in L. congesta; all reports of gemmae in L. congesta (e.g. Arnell 1963; Grolle 1969; Gradstein et al. 1983; Schuster 2021) are erroneous and refer to L. pansa.

Indonesia – West Java • “Pov. Preanger. In Cinchoneto “Daradjat” prope Garut ad terram. Regio nubium”; ± 1730 m; 2 Feb. 1894; c. marsup.; V. Schiffner 499; lectotype (designated here): FH [FH01122545]; isolectotypes: G [G00064407], JE.

Plants dioicous, 1–2 cm long, 0.5–2 mm wide, prostrate, somewhat dull-coloured (due to the densely papillose cuticle), pale green to olive green to light brown (shaded sites) or carmine red (exposed sites), shoots in strongly exposed sites worm-like with densely imbricate leaves, in shaded sites more flattened and with spreading, less densely imbricate leaves, stolons usually absent, when present located near the base of the shoot, leafy branches and innovations not observed. Stems ca 0.2–0.4 mm in diameter, fragile or rigid; dorsal surface green, ventral surface green or purplish-reddish; epidermal and medullary cells similar in size of the epidermal cells slightly smaller (Schuster 2021, as L. pansa), all cell walls thin (stems fragile) or walls of the epidermal cell walls slightly thickened (stems rigid). Rhizoids scattered, hyaline to light brown (to reddish or pink; Schuster 2021), with thin walls, sometimes with fungal hyphae. Leaves succubous, imbricate, unpigmented to partially or almost entirely brown to reddish pigmented, obliquely to widely spreading, subvertically arranged and appressed to spreading outwards or obliquely to widely spreading outwards, flat to convex to concave with convex margins, ovate-orbicular to broadly ovate to ovate-oblong (1.0–1.7:1), apex broadly rounded, margins entire, dorsal and ventral bases not or slightly decurrent. Leaf cells in the upper and dorsal part of leaf rounded-isodiametrical to slightly elongate, ca 20–30 µm in diameter, towards the margin similar in size or smaller, subquadrate, border of thicker-walled cells lacking, cells in the lower central and ventral part of the leaf distinctly enlarged, becoming 2–3× larger and more hyaline than in the upper part of leaf, isodiametrical to elongate, 1–4(–7)× longer than wide, becoming increasingly elongate towards the lower ventral margin; cells with distinct trigones, the trigones 3–8 µm in diameter, fully hyaline, sometimes reddish, with concave to slightly bulging sides, sometimes seemingly vanishing towards the ventral base, in the enlarged cells; cuticle of dorsal and ventral surface of leaf covered by low, hyaline, rounded to elongate papillae, the papillae becoming progressively more elongate towards the leaf base and sometimes rather inconspicuous in older herbarium material, when rounded ca 3–6 µm in diameter, cuticle at leaf margin smooth or with low papillae; oil bodies one per cell, greyish-brown, sometimes persistent in old herbarium material, finely papillose and sometimes with 1–2 pupils (“eye spots”), spherical to ellipsoid, 8–20(–25) µm long, ca 1/3–1/2 the length of the cell-lumen in the upper half of the leaf, in the lower half of the leaf cells only ca 1/5–1/4 the length of the lumen in the enlarged leaf cells. Underleaves not observed (Schuster 2021: occasionally present on some stems, ovate-elliptical to ligulate). Androecia with 5–6 pairs of bracts, bracts saccate, antheridia one per bract. Gynoecia as in L. pansa. Marsupia up to 10(–20) mm long, sometimes shorter (only ca 2.5 mm long in Pócs 01113/A from northern Queensland), outer surface hairy, wall 5–6 cells thick, marsupial canal lined by numerous large, somewhat clavate, papilliform cells, the cells up to 75 µm long, 13–20 µm wide, protruding from the mouth of the marsupium. Sporophytes (Schuster 2021) foot massive, with an extensive haustorial collar; seta long and slender; capsule narrowly cylindrical, hardly wider than the seta, slightly pointed or beaked at apex, opening by four valves. Gemmae positioned on the dorsal stem surface near the shoot apex, pale green, orbicular to slightly elongate, 4–10(–15) cells across, pale green to yellowish-brown, biconvex, centre up to 6 cells thick, towards the margin transparent, forming a 1(–2) cell wide unistratose wing, outer margin crenulate to irregularly crenate due to angularly protruding cells. Gemmalings originating from the margin of the gemmae.

Australasia (Australia, New Zealand, New Caledonia), Indonesia (Java), southern India (Kerala: Nilgiri Hills, Tamil Nadu). In Indonesia, L. javanica is known from two old collections from Java; its occurrence on soil along trails suggest that the species should be more common in Indonesia and has been overlooked. The true distribution of L. javanica and L. pansa in Australia and New Zealand requires more study and is beyond the limits of the present study. For the occurrence of L. javanica in India see Udar and Kumar (1986) and Alam (2014).

Lethocolea javanica grows on shaded and exposed sandy, loamy, or peaty soil, or soil over rock which dries out periodically, in rather xeric to humid vegetation, often along trails or water courses, from almost sea level to ca 1000 m in Australasia, and at 1700–2000 m in tropical Asia. In New Caledonia, the species occurs on basic, serpentine soil (pH 5–6) in maquis-type vegetation.

Australia – Australian Capital Territory (A.C.T.) • Canberra, Canberra National Herbarium, greenhouse collections; Cargill 1772; CANB • Canberra, Canberra National Herbarium, greenhouse collections; Purdie 12476; CANB. – New South Wales • Jimberoo State Forest, 11 km NNE of Rankin Springs; Curnow 3376; CANB [CANB9404956] • Cottan-Bimbang National Park, 0.5 km from Cells and 3 km from Oxley Highway; c. gemm.; Curnow 6163; CANB [CANB889563] • 19 km from Batemans Bay on Braidwood Road; 300 m; Streimann 970; CBG [CBG054175] • Weddin Mountain National Park, 16 km SW of Grenfell; Streimann 49251; CBG [CBG9213766]. – Northern Territory • NE Arnhem Land, Gore, Rindarry Creek; 40 m; Russell-Smith 4829; JE. – Queensland • Paluma Range, forest road 1–2 km N of Mt. Zero; 950 m; c. marsup.; Pócs 01113/A; GOET • Paluma Range, along Taravale forest road E of Mt. Zero; Cargill 165; CANB [CANB644649]. – Western Australia • Darling Range, forest at Martin, Mills Road, 22 km SE of Perth; Curnow 4793; CBG [CBG9512491] • D’Entrecasteaux National Park, 315 km S of Perth; Cargill 722; CANB [CANB759070].

New Zealand – North Island • “Forests of Titiokura” (Mitten 1854); c. marsup.; Colenso 3681, syntype of Gymnanthe drummondii Mitt.; NY [NY04461793] • Taupo; c. marsup.; Berggren 3141; NY [NY04461794] • Near Atiamuri; 1200 ft.; oil bodies persistent; Allison H259; JE • Hawkes Bay, Wairoa, Kiwi Valley; c. marsup.; Hodgson 6454; JE • Unuwahu bush; 300 m; Bartlett 2-79-4; JE • Ahipara; 200 m; Bartlett 195; JE •

New Caledonia – Grand Terre • Mont-Dore, near bifurcation of road Yaté–Plum; ca 100 m; c. andr.; Hürlimann 2001; GOET, PC • same data as for preceding; Hürlimann 2002; GOET, PC • East of Yanna valley near St. Louis; ca 150 m; Hürlimann 2013; GOET • same data as for preceding; Hürlimann 2033; GOET • Valley of Pouéta Kouré above La Coulée; 55 m; Hürlimann 2035; GOET, PC • Crest of Koghis Mts, SE of Mt. Bouo; 710 m; Hürlimann 2127; GOET, PC • Mt. des Sources; ca 800 m; Hürlimann 2354; GOET, PC • Dumbéa, near “Sunshine” mine; ca 650 m; c. gemm., oil bodies persistent; Hürlimann 2409; GOET.

Indonesia – Java • Central Java, Salangan; 1924; c. gemm.; Goebel s.n.; JE.

Lethocolea javanica is recognized by the densely papillose cuticle, distinct trigones in the middle and upper part of the leaves, and winged gemmae with a crenulate to crenate margin of slightly to strongly and angularly protruding cells. In Australasia, the species has previously been called L. pansa (e.g. Engel and Glenny 2019; Schuster 2021), but the latter species has a smooth cuticle, minute trigones, and wingless gemmae with a crenulate margin of slightly and regularly bulging cells that are not protruding angularly (Figs 3–5). The status of the two species is confirmed by the molecular analysis (Fig. 2). The detailed description and illustration of L. pansa in Engel and Glenny (2019) is a mixture of L. pansa and L. javanica. In older herbarium material, the papillae of L. javanica may sometimes become somewhat inconspicuous and some authors have described the cuticle as being smooth (e.g. Schiffner 1900; but see Stephani 1901). Schiffner (1898) also suggested that trigones are absent in the type of L. javanica (“Trigonis nullis”), but we observed distinct trigones in the type material.

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.

Furuki (2001: fig. 1).

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.

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

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.

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.

Symphyomitra glossophylla Spruce (= L. congesta (Lehm.) S.W.Arnell).

Stems ventral surface green to brownish-green, stolons present or absent. Leaf cells with a densely papillose cuticle; oil bodies 1–3 per cell (usually 2), dark brown, often persistent in plants with distinct trigones (Fig. 3G, H), ellipsoid to fusiform, 8–10 × 15–25 µm, brown, finely papillose, pupils (“eye spots”) absent. Antheridia 1(–6) per bract. Marsupia short-cylindrical, up to 3 mm long, wall 5–6 cells thick, marsupial canal lined by few papilliform cells (Grolle 1972). Capsules splitting to the base into 2–4 valves, with two adjacent valves sometimes remaining partially connate. Asexual reproduction by disciform gemmae absent.

One species in Africa, Central and South America, and on the south Atlantic Islands.

South Africa – Western Cape Province • Tafelberg; Ecklon s.n.; lectotype (designated here): S [B25217]; isolectotypes: S [B25218], S [B25221], S [B25222], G [G00115872], G [G00115873], G [G00115874], JE, W [2010-01828].

Plants dioicous, 1–2 cm long, 1–3(–4) mm wide, creeping or ascending, dull, pale to rather dark green to yellowish-green to yellowish-brown, becoming more pale-coloured and transparent on older shoot portions; branching ventral-intercalary and stoloniform or (rarely) lateral-intercalary and leafy, stolons usually near the base of the stem, occasionally higher up the stem and sometimes originating from below the immature marsupium. Stems fragile to rigid, colourless or pale green to brownish-green (never purplish-reddish), 0.25–0.5 mm in diameter, made up of 190–290 thin-walled cells. Rhizoids scattered or slightly fascicled, hyaline to light brown. Leaves present throughout the stem or limited to the upper portion of stem (the lower portion of stem thus stoloniform), green or occasionally tinged purple or red, densely imbricate and upright when growing exposed, more loosely imbricate or distant and spreading when growing in shade, towards the shoot apex usually upright and appressed, obliquely to widely spreading on older stem portion, suborbicular to ovate-oblong to oblong to lingulate, widest at 1/3–1/2 of leaf length, 0.8–2.1 mm long, 0.8–1.4 mm wide, 1–2.2× longer than wide, flat in upper half and concave-convex in the lower half, apex usually rounded, occasionally truncate to emarginate, dorsal margin straight or slightly narrowed to the base, ventral margin arched and slightly to distinctly narrowed to the base, dorsal base shortly to moderately decurrent, ventral base not decurrent, lamina more transparent in the lower ventral half of the leaf due to larger cells with little or no chlorophyll. Cells in midleaf isodiametric-hexagonal to slightly elongate, 25–50(–60) × 20–40 µm, at the leaf margin slightly smaller and quadrate to rectangular, thin-walled, sometimes thick-walled and forming a border in plants with conspicuous trigones; cells in the lower ventral half of the leaf more hyaline, enlarged and elongate, about 2–4× longer than wide, 40–100 × 20–40 µm, becoming gradually narrower and more elongate towards the margin, to 6× longer than wide, 2–10 cell rows along the lower ventral margin without chlorophyll and in part lacking oil bodies, enlarged hyaline cells may extend high up in the ventral half of the leaf and sometimes in the upper half to near the apex (in plants from dry, Mediterranean environments); cuticle papillose both dorsally and ventrally, papillae colourless, rounded to suboblong, 2–5(–10) × 2–3(–8) µm, becoming more elongate to linear on the cells in the lower ventral half of the leaf; cell walls with minute to large trigones, the trigones to 10 µm in diameter, with concave to slightly bulging walls, not confluent (except sometimes on short cell walls); oil bodies 1–3 per cell, dark brown, persistent in rather rigid plants with distinct trigones (seen in up to 100 years old herbarium specimens), vanishing in flaccid plants with minute trigones, ellipsoid to fusiform, 2–3× longer than wide, 8–10 × 15–25 µm, finely granular. Androecia terminal or intercalary, bracts in (1–)3–20 pairs, rather similar to vegetative leaves but more deeply pouched towards the base and with dorsal margin incurved; antheridia 1(–6) per bract. Gynoecia terminal on a main shoot, when unfertilized often with a ventral branch, bracts as large as or slightly larger than vegetative leaves, usually upright and appressed, in gynoecia with mature marsupia sometimes slightly spreading outwards. Marsupia conical-subcylindrical, green when young, brown when mature and with a hairy surface, up to 3 mm long, 2.5–3× longer than wide, tapered towards the tip (tip not swollen). Sporophytes foot embedded inside the marsupium, elongated seta and capsule long-exserted; seta whitish, up to 1.2 cm long after elongation, formed by ca 70 cell rows, cells isodiametrical to somewhat elongate, with small trigones, the trigones of outer cell walls more conspicuous; capsule (before dehiscence) dark brown, cylindrical, tip apiculate, with four dehiscence lines, upon dehiscence splitting to the base into four valves or into only 2–3 valves with two adjacent valves remaining partially connate, valves erect, 1.5–3.0 × 0.7–1.0 mm, wall 2(–4)-stratose, being mostly 2-stratose with limited 3–4-stratose areas (Fig. 9F), cells of the outer layer quadrate to long-rectangular, 37–100 × 18–32 µm, walls thin but firm, yellowish to reddish-brown, with small, orange to reddish-brown, nodular thickenings evenly spaced along the longitudinal walls, turning into conspicuous thickening bands on radial walls, cells of the inner layers variable in shape and size, trapezoidal-elongate, rounded-rectangular to rounded-quadrate, 37–85 × 28–40 µm, walls thin, hyaline, without thickenings; elaters with 1–2 spirals, narrowly fusiform, 130–200 × ca 10 µm, narrowed toward the tips, the tips rounded, surface finely punctate; spores (from herbarium material soaked in water) isodiametrical, ca 25 µm in diameter, yellowish to brown, spore surface finely papillose. Gemmae absent.

In high mountain areas of tropical America (Mexico to Bolivia, southeastern Brazil, Dominican Republic) and tropical Africa (Central and East Africa, Réunion), furthermore in Mediterranean and temperate areas of southern South America (especially Chile), on the south Atlantic Islands (Tristan da Cunha, Prince Edwards Is., Crozet Is.), and in South Africa.

Lethocolea congesta grows on moist soil along trails, on earth banks, and near rivulets, as well as on soil over acidic and lava rock, exceptionally on tree bases. In tropical regions, the species occurs in montane and subalpine forest areas and páramó, at (1000–)2000–4500 m, in Mediterranean and temperate regions in scrubby vegetation, often rather xerophytic, from sea level to 1000 m.

Mexico – Mexico • Passo Puerto de la Cruces; 3000 m; Düll 21332; JE.

Costa Rica – Cartago • Cordillera de Talamanca, near Panamerican highway; 3350 m; van Melick 214515; PC • Chirripó; 3550 m; Kuhbier 627; JE • Páramo Buena Vista; 3250 m; Holz CR2009; GOET.

Venezuela – Mérida • Páramo de Mucuché; 3300–3700 m; c. gyn.; Griffin PV395; GOET • Páramo de Mucubaji; 3500–3600 m; Drehwald 40133; GOET.

Colombia – Boyacá • Sierra Nevada del Cocuy, Corralitos; 3900 m; c. gyn.; Bischler 2881; G, PC • same data as for preceding; 4000 m; Bischler 2997; G, PC • Sierra Nevada del Cocuy, near laguna La Pintada; 4300–4700 m; Bischler 2829; PC. – Caldas • Nevado del Ruiz; 4200 m; Bischler 291; G, PC • same data as for preceding; 3780 m; c. gyn.; Florschütz 4396; GOET • ibid., near hotel Termales; 3460 m; Cleef 2386; GOET. – Cauca • Páramo de las Papas; 3200–3600 m; Bischler 918; GOET. – Cundinamarca • Páramo de Chingaza; 3460 m; c. gyn. & andr.; Gradstein 4249; GOET. – Risaralda • Parque de los Nevados, Páramo de Santa Rosa; Aguirre et al. 4875; GOET • same data as for preceding; Aguirre et al. 4952; GOET.

Ecuador – Carchi • Páramo El Angel; 3400 m; c. andr.; Arts 14/067; QCA • same data as for preceding; 3300–3630 m; Gradstein et al. 3349; GOET • same data as for preceding; Gradstein et al. 6834; GOET. – Cotopaxi • Parque Nacional Llanganates, vicinity of Laguna Anteojos; 4000 m; Burghardt et al. MB6806; PC • Near Sindipamba; c. gyn.; Arts 23/005c; JE • Cotopaxi National Park, along road near the Park entrance; 3550 m; Gradstein & Frahm 6667; GOET. – Pichincha • Road Lloa – Río Cristal; Gradstein & Frahm 6698; G, GOET • Old road Quito to St. Domingo, W of San Juan; ca 3000 m; Gradstein et al. 6720; GOET • Quito, Parque Metropolitano; 2800 m; Burghardt 6555; QCA. – Zamora-Chinchipe • Podocarpus Nat. Park, Río Bombuscara; 1000 m; Schäfer-Verwimp & Preussing 23417; GOET.

Peru – Apurimac • Huancaras; 3700 m; c. marsup.; Hegewald 5708; JE. – La Libertad • Road to Otuzco, near Esquil; leaves bordered; Hegewald 7197; JE.

Bolivia • Torreni-Yamakaka; ca 4500 m; leaves partially bordered; Herzog 3739; JE. – Cochabamba • Incachaca; 3400 m; Gradstein 7397; GOET. – Santa Cruz • Near Vallegrande; 2500 m; Churchill 22308; MO, GOET.

Chile – Juan Fernandez Islands • Masafuera; ca 400 m; Hatcher & Engel 48; JE. – Coquimbo • Fray Jorge; Schwabe 227; JE. – Valparaíso • Nature Reserve La Campana; ca 500 m; Gradstein & Cuvertino 12426-B; PC • same data as for preceding; Larrain 43934; BR • same data as for preceding; Larrain 43937; BR • La Ligua; 458 m; Larrain 45507; BR • Viňa del Mar; Larrain 40415; BR • Laguna Peñuelas; 380 m; Mahu 13006; JE, MO, PC • El Tabo; 20 m; Mahu 11862; JE. – Metropolitana • Reserva Altos de Cantillana; 1869 m; Larrain 43526; BR • Laguna de Aculeo; Mahu 21984; JE. – Libertador • Sierras de Bellavista; 1600 m; Mahu 20139; JE, MO. – Maule • Talca; 1230 m; Mahu 50004; MO • Talca; 1230 m; Mahu 50060; MO • Linares; 764 m; Larrain 42566; BR. – Nuble • San Fabian; between Leptoscyphus expansus; 250 m; Mahu 9310; MO. – Araucanía • Cerro Lungoico, 1000 m, Schwabe 109; JE • Pucón; Mahu 11501; JE, MO • Volcán Villarica; Hosseus 211; JE. – Los Ríos • Corrál; 10 m; Mahu 13559; JE • Niebla; 30 m; Mahu 12007; JE. – Los Lagos • Llanguihue, Yerbas Buenas, near Area de Recreación Las Cascadas; 20 m; c. marsup.; Mahu 21410; MO • same date as for preceding; 20 m; c. marsup.; Mahu 21438; MO. – Chiloë • Quicavi; c. marsup. & spor.; Halle 139; JE. – Tierra del Fuego • Isla Grande, Cerro Recalada; Hyvönen 32212; JE.

Argentina – Chubut • Parque Nacional Los Alerces, Alerzal; 560 m; Hyvönen 5502a; JE.

Democratic Republic of Congo – Lacs Edouard et Kivu • Mt. Karisimbi; 3400 m; De Sloover 13131; BR [BR5040101618594] • same data as for preceding; De Sloover 13150; BR [BR5040264975688].

Rwanda – Lacs Edouard et Kivu • Mt. Muhavura; ca 3900 m; De Sloover 13634; BR [BR5040264976692] • Mt. Karisimbi, Hagenia forest; Frahm 8048; G.

Uganda • Kigezi; c. gyn. & andr.; Hedberg 2156; BR [BR5040101615562] • Ruwenzori, Lac Mahoma; 3050 m; Lisowski 2984; BR [BR5040034019697].

Kenya • Mt. Kenya, NW slopes; 3450 m; Hedberg 1990a; JE • Moru track; 3800 m; Agnew 345; JE.

Tanzania • Mt. Kilimanjaro, Makoa River below Machame hut; 2960 m; Pócs 6976/AH; G • ibid., trail Madara hut to Horombo hut; 3400 m; Albertshofer s.n.; JE • ibid., Shira Plateau; 4000 m; Lewinsky B627; BR [BR5040264971642] • South Uluguru Mts, gorge of Mgeta River; 2215–2370 m; Pócs 6829/J; G, JE, PC • Mt. Meru, Engare Narok gorge; 2490 m; Pócs & Kis 9145/A; GOET.

Réunion • Plaine des Cafres; 1570–1600 m; Onraedt 74R8378; JE • Sentier de Langevin; 2100 m; Onraedt 71R7573; BR [BR5040235549337]; JE • Forêt du Taibit; ca 2000 m; leaves bordered; Onraedt 74.R.8687; JE • Forêt du Taibit; 1750 m; leaves bordered; Onraedt 75R942; BR [BR5040235558421] • Footpath to La Nouvelle; 1610 m; Arts 61/69; BR [BR5040315946179] • Cirque de Cilaos; 1600 m; leaves bordered; Onraedt 73R1229; BR [BR5040235550340] • Sentier vers Piton des Neiges; 1550 m; leaves bordered; Arts 19/54; BR [BR5040315939102] • same data as for preceding; 2000 m; c. marsup.; Onraedt 70R4530; JE • Trail to Piton de la Fournaise, Pas de Bellecombe; Onraedt 69R330; BR [BR5040101616576], JE • Pas des Sables, between Bourg Murat and Piton de la Fournaise; 2320 m; Arts 42/04; BR [BR5040315941129].

South Africa – Natal • Drakensberg Gardens, near Wilson’s Cave; Meyer 1052c; GOET • Bergville Division, Drakensberg, Injasuti area; 5000–9000 ft.; Esterhuysen 26104; BOL • ibid., Ndederna area; 6000 ft.; Esterhuysen 22986; BOL. – Western Cape Province • W of Cape Town, NW slope of Devils Peak; 300–400 m; Rolfe 81; JE • Constantia slopes; leaves bordered; Arnell 375; BOL • Jeep track from Constantia Neck to Table Mountain; 300–700 m; leaves bordered; Arts 129/02; BR [BR5040313690890] • same data as for preceding; Arts 129/43; BR [BR5040313688873] • Kasteel Poort; Arnell 1103; JE • Between Kloof Nek and Brinkwater Ravine; Arnell 1104, paratype of Symphyomitra tabularis; BOL [BOL0233665] • Kirstenbosch & Kloof Nek; Bottomley 212, as Odontoschisma sphagni; PRE, S • Kirstenbosch; Esterhuysen 2; BOL • same data as for preceding; Vanden Berghen s.n.; BR [BR5040034017679] • Camps Bay; Garside 6681; BOL • Ceres Division, Hansiesberg; ca 1250 m; Esterhuysen 25689; BOL.

Lethocolea congesta is a widely distributed and highly variable, Afro-American species that has been described under many different names. In tropical America, the species was known as L. glossophylla and in southern South America and on the south Atlantic Islands as L. radicosa. Both appear to be synonyms of L. congesta. Lethocolea congesta differs from the other members of the genus in having 1–3 (usually 2) dark brown oil bodies per cell (Fig. 3G, H) and in lacking asexual reproduction by disciform gemmae. Moreover, the marsupia are shorter, maximally 3 mm long and conical-subcylindrical in shape (Fig. 9A, C, E), and the marsupial canal is lined by few papilliform cells.

The leaves in Lethocolea congesta range from suborbicular to ovate-oblong to narrowly lingulate and the area of enlarged, hyaline cells in the ventral half of the leaf may be restricted to the base or extending upwards, exceptionally to near the leaf apex. The hyaline area in the leaf is usually more extensive in Mediterranean plants from low elevation than in the plants from high elevation in the Tropics. The cuticle of the leaf cells is densely papillose, although the crowding of the papillae may vary somewhat (Fig. 3A, D), and the trigones may be very small, ca 1 mm in diameter, or well-developed, up to 10 µm in diameter (Fig. 8G, H). The size of the trigones seems to correlate with elevation as well and is usually smaller in plants from low elevation than from high elevation. The latter plants are usually more rigid (and easier to dissect) than those from low elevation and herbarium specimens from high elevation often had well-preserved oil bodies (Fig. 3G, H), which were found intact in up to one hundred years old dried material. In herbarium specimens from low elevation, in contrast, oil bodies had usually vanished.

The thickening of the walls of the leaf margin cells is normally similar to that of the inner leaf cells (Fig. 8D, F). In some specimens, however, they were thicker-walled (by confluent trigones) than the inner cells, forming a thickened border extending along part of, or almost the entire leaf margin (Fig. 8B, C). Leaf borders of thick-walled cells occur in several genera of liverworts, e.g. in Adelanthus Mitt., Bazzania Gray, Calypogeia Raddi, Odontoschisma (Dumort.) Dumort., Plagiochila (Dumort.) Dumort., Scapania (Dumort.) Dumort., and Radula Dumort., and can be a useful and stable taxonomic character to distinguish species (Oliveira da Silva et al. 2022). In L. congesta, however, the development of a border – seen in specimens from throughout the range of the species – was variable and appeared to be without taxonomic relevance as no correlation with other characters was observed.

Figure 7. 

Lethocolea congesta. A. Shoot. B–H. Leaves. I. Leaf insertion, dorsal view. J. Shoot, ventral view. K–L. Shoot, dorsal view. A, D, J–K from Holz 209; B from Gradstein 10165; C, E from Arts 129/02; F–G, L from Arts 19/54; H–I from Larrain 42566. Drawn by Anna Luiza Ilkiu-Borges.

Figure 8. 

Lethocolea congesta. A. Leaf. B. Margin cells near ventral leaf base, showing border. C. Margin cells near dorsal leaf base, showing border. D. Margin cells near ventral leaf base. E. Margin cells at leaf apex. F. Margin cells near dorsal leaf base. G. Midleaf cells. H. Midleaf cells. A, F–G from Gradstein 10165; B from Holz 209; C–E, H from Arts 129/02. Drawn by Anna Luiza Ilkiu-Borges.

Figure 9. 

Lethocolea congesta. A, E. Female shoot with near-mature marsupium. B. Elater. C. Shoot apex with mature marsupium, female bracts and mature sporophyte before dehiscence, showing apiculate capsule. D. Cross section of seta. F. Cross sections of capsule. G. Outer cells of capsule wall, frontal view. H. Outer cells of capsule wall, lateral view. I. Inner cells of capsule wall, frontal view. J. Spores. K. Male bract with antheridium. L. Male plant with androecia. M. Cross section of stem. A from Onraedt 70.R.4539; B–J from Halle 139; K–L from Larrain 45507; M from Holz 209. Drawn by Anna Luiza Ilkiu-Borges.

Young gynoecia with very short, bulging marsupia were not uncommon and were most frequently seen in plants from exposed sites. The female bracts are normally upright and tightly appressed, but in in gynoecia with fully grown marsupia they were sometimes spreading outwards. One or two innovations may sprout from the bulging base of young gynoecia. Mature marsupia and sporophytes are rare and were only seen in two old collections from Chile, i.e. Valparaiso, Gay s.n. (type of Gymnanthe bustillosii Mont.) and Chiloë I., Halle 139 (Fig. 9B–I). Spruce (1885) provided a detailed description of the mature marsupium and sporophyte in L. glossophylla based on the type collection from Ecuador. However, plants with marsupia could not be found in the type material of L. glossophylla kept in the Spruce herbarium (MANCH). A peculiar feature of the capsule of L. congesta is that dehiscence is sometimes incomplete, with capsules splitting to the base into only 2–3 valves (instead of 4 valves) with two adjacent valves remaining partially connate.

Male plants were less frequent than female plants. The length of the male spikes appeared to be highly variable, of 1–20 consecutive pairs. In a few instances male and female plants were found growing mixed (e.g. Uganda, Hedberg 2156; Colombia, Gradstein 4249); nevertheless, no sporophytes were observed in these specimens.

Several authors have suggested the occurrence of gemmae in African Lethocolea congesta (e.g. Arnell 1963; Grolle 1969; Gradstein et al. 1983; Schuster 2021). These reports are erroneous and were based on Arnell (1963) who included gemmiferous plants belonging to L. pansa in his treatment of L. congesta (this study). It has also been suggested that L. congesta is paroicous (based, again, on Arnell (1963) who wrote “Paroicous?”), but no paroicous plants of L. congesta have been seen in this study.

In the Neotropics, L. congesta has been confused with Solenostoma amplexifolium, but the latter species has a smooth cuticle and also lacks an area of elongated, hyaline leaf cells. Moreover, the rhizoids in S. amplexifolium are usually reddish or brown (rarely hyaline), the leaves are concave with the dorsal base clasping the stem (rarely plane, e.g. Mexico, Burghardt 4495, identified as L. glossophylla), and the oil bodies are colourless and not persistent.

Stephani (1906: 222) erroneously placed Lethocolea congesta in synonymy of Leptoscyphus expansus (Lehm.) Grolle. The latter species often grows mixed with L. congesta in Chile and South Africa, on earth banks, and superficially resembles L. congesta in habit. The presence of underleaves with rhizoids sprouting in bundles from underleaf bases, and the absence of an area of elongated hyaline cells in the lower ventral half of the leaf clearly separate sterile material of Leptoscyphus expansus from L. congesta.

Symphyomitra tabularis is tentatively placed here in synonymy of L. congesta following Arnell (1955, 1963). The synonymy needs verification as the original description of S. tabularis (Arnell 1953) was a combination of L. congesta and L. pansa. The leaves tinged purple, the papillose cuticle, and the presence of 1–3 oil bodies per leaf cell mentioned in the protologue of S. tabularis are characters of L. congesta, but the disciform, wingless gemmae mentioned in the original description point to L. pansa. The description of S. tabularis was used almost unaltered in the treatment of L. congesta in the South African hepatic Flora (Arnell 1963). We have been unable to study the type of S. tabularis, which was deposited in BOL and S (Arnell 1953). The isotype in BOL is apparently missing (Cornelia Klak pers. comm.) and the type material in S – which is present there according to the database of S – is currently unavailable due to the renovation of the Stockholm herbarium. Arnell (1953), additionally, cited four paratype collections, two from Constantia slopes and two from Kasteel Poort. We have examined the two paratype specimens from Kasteel Poort based on duplicates kept in BOL and G; one of them belongs to L. pansa (Arnell 1036, G), the other is L. congesta (Arnell 1104, BOL). In addition, numerous non-type specimens have been examined from Constantia slopes, collected by Arnell and others, where Lethocolea seems to be common. These collections also included both species. It may thus well be possible that the type of S. tabularis belongs to L. pansa rather than L. congesta.