Plants usually small to medium(main shoots 600–1100 µm wide), forming olive-green to reddish brown patches, closely to loosely adhering to substrate. Leading stem 10–20 mm long and 100–170 µm in diam., 8–10 cells wide; ± 20 cortical cells + 25 medullary cells, cortical cells occasionally slightly smaller than medullary cells, otherwise little differentiation between them, both cells with ± thin walls (not heavily thickened as usually the case in Frullania stem cells), lumen irregularly shaped. Branching often irregularly pinnate, occasionally 2-pinnate; the branches elongate and similar to main stem, of Frullania-type. First branch underleaf (BUL1) usually with two distinct segments, 1 large unlobed ventral segment (to 250 µm long) + 1 slightly smaller dorsal segment (to 200 µm long); occasionally BUL1 with three distinct segments, 1 ventral bilobed + 1dorsal, explanate to at most sulcate segment. First branch leaf (BL1) usually characteristic of main stem leaves except the dorsal lobe may be reduced and strap-shaped. Stemleavesof main branchflat when both dry and wet, slightly imbricate to contiguous, occasionally remote, (350)450–650(800) µm long ×(300)420–600(750) µm wide, ovate to suborbicular, occasionally narrowly incurved from apex to ventral margin, dorsal margin extending beyond the farther edge of the stem (0.5–1Χ the stem width), apices rounded to obtuse, dorsal base arched and rounded to weakly auriculate at the base; surface smooth; margins entire. Lobules variable: in well-formed plants the lobules are ± equally inflated throughout, typically medium in size, often 0.25 to 0.5Χ the exposed area of the associated leaf-lobe, often galeate and ± as long as wide or slightly longer than wide, occasionally oblate, (180)200–350(400) µm long × (130)190–320(390) µm wide, at broadest region the lobule up to 35 cells in circumference, lobule beak absent or at most poorly developed, free margin of lobular mouth truncate or slightly arched and to 20 cells in length, lobule apex broadly rounded; the lobules of poorly developed plants may be explanate or sulcate, lanceolate, to 120 µm long × 50 µm wide. Stylus usually minute to small, filiform to narrowly triangular, (40)50–80(100) µm long, 1–2 (3) cells wide at base and when filiform with a uniseriaterow of 2–4 cells, (3)4–6(7) cells in total, usually with an elongated slime papilla at apex (to 16 µm long).Underleaves of leading stems small to medium in size (ca. 0.25 the size of leaf lobes), flat and closely appressed to stem, slightly contiguous to and rarely overlapping the lobules, underleaves usually distant from each other, often suborbicular in outline, usually as long as wide (some phenotypes 1.5Χ long as wide and obcuneate), (175)190–250(300) µm long× (150)175–225(280) µm wide, broadest at middle (to 25 cells wide); margins vary, entire or often with a short, triangular, blunt tooth or angle on shoulders of lateral margins; apex of underleaf bilobed 0.3–0.5 its length, lobes separated by a narrowly U to V-shaped sinus, lobes triangular with acute to narrowly obtuse apices; insertion transverse. Rhizoid-initial area ranges from just below underleaf sinus or near middle to base of underleaf, rhizoids frequent, fasciculate, brown pigmented, long (to 400 µm long). Plants not microphyllous, organs of secondary branches similar in size to those of the main stem.
Lobe median cells with variable walls, some phenotypes with thin, semi-straight and hyaline walls, and small, subtriangular trigones and occasionally small ± nodulose intermediate thickenings, other phenotypes (occasionally even on other leaf-lobes of the same plant) walls becoming sinuose with confluent trigones and with small nodulose intermediate thickenings, hyaline along the middle lamellae, with dark reddish brown pigmented secondary thickening, the cell cavities of median cells brownish red, (8)12–25(30) µm long × (8)12–20(24) µm wide, becoming gradually larger basally; lobe basal cells ± thin walls with subtriangular to nodulose trigones and occasionally with intermediate thickenings, the cavities of the basal median group of cells (25)30–40(43) µm long × (15)20–30(35) µm wide; lobe marginal cells with ± equally thickened, hyaline walls, ± rectangular to subquadrate, the cell cavities brownish red, 8–16 µm long × 8–14 µm wide. Underleaf median cells with ± equally thickened, semi-straight walls, with small intermediate thickenings or slightly sinuose due to confluent trigones and intermediate thickenings, the cell cavities (12)20–30 µm long × (12)15–25 µm wide. Lobulemedian cells with strongly sinuose walls with indistinct trigones and small nodulose intermediate thickenings, the cell cavities slightly longer than wide, 12–20 µm long × 8–12 µm wide. Asexual reproduction occasionally via caducous leaf lobes and less often lobules, which may develop propagula before dehiscence or occasionally via ± discoid gemmae from the leaf lobe margins.
Dioicous. ♂ Plants slightly smaller (shoots to 800 µm wide) than ♀ plants. Androecia discoid (400 µm long × 400 µm wide) to spicate (900 µm long × 500 µm wide), 3–10(12) pairs of bracts, sessile or terminal on very short-stalked branches (stalk with 1–2, rarely 3 modified vegetative leaf lobes). Gynoecia terminal on main stem and branches, often bearing 1 subfloral innovation, developing in place of the outermost bract-lobule below the gynoecium. ♀ Bracts and bracteoles in 2–3 closely imbricate cycles. Innermost bract unequally bifid; lobe elliptical to ovate, becoming narrowed toward a rounded apex, the margin entire; lobule lanceolate, subacute at the apex, margin entire except for a large tooth at the base and usually a second smaller 2–4 celled tooth terminating in a slime papilla. Innermost bracteole connate with innermost bract, oblong to oval in outline, about 0.3 to 0.5 bilobed, the sinus acute, lobes acute at apex, with 1–2 teeth on the free margins. Median cells of bract: walls thin, semi-straight to nearly sinuose, indistinct trigones with small intermediate thickenings; cell cavities to 15 µm long × 15 µm wide. Two to three archegonia per gynoecium. Perianth freely emergent, (750)900–1350(1500) µm long × (600)700–1000(1200) µm wide, often pyriform or obovoid, usually tapering abruptly towards the apex into a short beak; perianth beak cylindrical, to 80 µm long × 60 µm, with a smooth mouth and inner surface. Perianth varying in the formation of ventral and dorsal keels. Typical phenotypes have 2 large lateral keels + 1 dorsal keel + 2 ventral keels; thus 5-keeled in transverse profile; all keels occurring from perianth base to apex. Margins of keels smooth and ± sharp, or occasionally developing at most a few inconspicuous, irregular and shallow tubercles or projections towards base of perianth. Other phenotypes with 2 large lateral keels + 2–3 ventral keels (occasionally with 1–2 additional accessory keels) + 1–2 dorsal keels; thus 6 to 9-keeled in transverse profile. Accessory keels not reaching apex of perianth; margins of all keels vary from smooth and sharp to ± flexuose, occasionally developing a few inconspicuous, irregular and shallow tubercles or projections towards base of perianth. Median cells of perianth: walls thin, semi-straight to nearly sinuose, trigones concave with small intermediate thickenings (when sinuose, trigones and intermediate thickenings becoming ± nodulose), the cell cavities to 25 µm long × 16 µm wide.
Capsule valves to 700 µm long × 450 µm wide; inner cell layer withthe thickenings appearing as a network-like configuration across the face, surface with ridges along the individual cells, the cell surface under sem with fine granular perforations (250–400 nm in diameter). Elaters to 80or more in total (arranged in 5–6 rows along valve), the surface under sem irregularly rugose-granulate. Spores globose, to 30 µm at the widest axis, which is interspersed with 6–8(9) rosettes, the rosettes each 2.5–4 µm in diam., and bearing a ring of (4)6–8(9) irregular, elongate protuberances; protuberances ± smooth, baculate to tuberculate, ca.1–1.75Χ long as wide, usually 0.75–1.75 µm long × 0.75–1 µm wide, gradually tapering to a rounded apex or with subparallel sides and subtruncate to obtuse at apex; spore wall papillae otherwise densely distributed between rosettes.
Affinities, differentiation & variation:
By arguing that F. probosciphora be reduced to a subspecies of F. pentapleura, Hattori (1988) implied a close relationship between these two taxa. However, as detailed above there would appear to be sufficient differences for them both to be recognised at the species level at this stage. Listed in Table 7.5 is a suite of characters that can be used to differentiate between the two taxa. Morphologically, F. pentapleura, in its strictest form, more closely resembles the New Zealand taxon, F. solanderiana. In fact, much of the variation encountered in F. pentapleura may also be found in F. solanderiana; the taxonomic relationship between these two species is under investigation.
Frullania pentapleura is a variable species with several forms frequently encountered. These can be broadly categorised on the basis of features associated with the perianth, cell wall anatomy of the leaf lobe, and the presence or absence of gemmae and caducous leaves. Based on the perianth, there are basically two forms: those that have 5 keels and those with greater than 5 keels, rarely both forms of perianth occur on the same plant. Similarly, there are also two forms based on the cell-wall anatomy of the leaf lobe. Some specimens have semi-straight cell walls whilst others have nodulose cell walls, but there are also variants with both types of cell-wall patterns on the same plant. Finally, there are some forms with gemmae and or caducous leaf lobes (e.g. CBG 8002286), and also those without any form of asexual reproduction.
Australia (ACT, New South Wales, Queensland, Victoria) but no confirmed reports from Tasmania, and New Zealand. Hattori (1983) stated that Rodway (1916) mistakenly reported F. pentapleura for Tasmania, and that Rodway’s material must be considered as F. probosciphora because it was described as ‘perianth 3-5 ribbed on both surfaces’. Frullania pentapleura could possibly be considered as a generalist species growing in a range of habitats and grows on both bark and rock. Like many species of Frullania, pigmentation and some morphological features of F. pentapleura may vary according to environmental factors; in moist shaded habitats the plants are often olive green, have leaf lobes with semi-straight cell walls, and inflated lobules; in dry, more exposed habitats the plants are often red to dark brown, have caducous dorsal leaf lobes, and with nodulose cell walls. Ratkowsky (1987) recorded F. pentapleura in a checklist of Tasmanian liverworts, but this is not confirmed.
Notes: Hattori (1979a) suggested that F. wildii Steph. was possibly conspecific with F. pentapleura. Examination of the F. wildii type material and a range of F. pentapleura material revealed that the former falls within the variation of the latter and F. wildii is therefore reduced to synonymy.