Plants small to medium, main shoots ca. 300 to 600 µm wide), forming olive-green to occasionally almost copper-brown patches, closely to loosely adhering to substrate. Leading stem to 50 (75) µm in diam., 5–7 cells wide, little differentiation between cortical cells (to 10 in no.) and medullary cells (6–8 in no.), former slightly smaller than the latter, both with firm walls, lumen irregularly shaped. Branching of Lejeunea-type (LB) and Frullania-type (FB). Initial appendages of LB always reduced in size, strap-like, and lobule-free, normal stem leaves frequently initiate at BL3 or BL4, otherwise from either BL5–BL8. Initial appendages of FB vary, either i) frequently BUL1 of 1 ventral, explanate, bilobed segment + 1 dorsal saccate segment; BL1: 1 explanate dorsal lobe + 1 saccate lobule + 1 stylus (i.e. ± characteristic of normal stem leaves); or less often ii) BUL1 of 1 ventral bilobed (to almost bifid in some cases) + 1 ventral, explanate to at most sulcate segment, segments large and extending beyond the lobes or segments of BL1 and/or reaching the segments of BL2; BL1: 1 ventral saccate segment + 1 dorsal explanate segment ± stylus; or iii) BUL1 of 1 ventral, explanate, bilobed segment + 1 dorsal saccate segment; and BL1: 1 explanate lingulate segment + 1 lanceolate segment + stylus, often reduced in size in comparison to normal stem leaves; leaves characteristic of normal stem leaves starting at BL2 or occasionally not until BL4. Stemleavesof main branchflat when dry and wet, sub remote to imbricate, suborbicular to broadly oval, to 225 µm long X 200 µm wide, and dorsal margins extending beyond the farther edge of the stem; rounded to acute apices and non-auriculate at the base, but apices of young shoots often apiculate of 1–2(3) cells; surface smooth; margin delicately crenulate-denticulate or denticulate, the teeth formed by partially projecting single cells. Lobules ± remote from the stem, typically at angles of ca. 45º with the stem so that lobules tilted outwards; cylindrically pitcher-shaped, relatively large, occupying ca. 0.5x the exposed area of the dorsal leaf-lobe, 1.75–2 x as long as wide, to 175 (225) µm long X 90 (115) µm wide; somewhat dorsiventrally compressed near mouth as compared to gibbous upper half, the opening wide, extending along the abaxial lobule margin; immediately above lobule mouth there is a ± discoloured, gibbous cell, with the free wall conspicuously thick, cell cavity ca. 2X long as wide, to 15 µm long. Stylus small to medium in comparison to leaf-lobule, subtriangular, of up to 15 cells in total. Underleaves of leading stems, distant, small, to 150 µm long X 80 µm wide, as wide as stem or only to 1.25X the width of stem, broadest at middle, 5 –8 cells wide, underleaf to 12 cells in length, bilobed to ½ its length, lobes separated by a narrowly U to V-shaped sinus, lobes ± lanceolate, entire, lobes only 2–4 cells wide.
Lobe marginal cells ± subrectangular to subquadrate, free tangential walls often drawn out as a thick-walled tubercle, otherwise walls subequally thickened; median cells ± subquadrate to rectangular, hyaline walls subequally thickened, intermediate thickening rare to absent, cell cavities of median cells to 10–15 µm long X 8–12 µm wide; cells becoming gradually larger basally, to 20 µm long X 15 µm wide. Median cells of underleaves ± subequally thickened so that the hyaline trigones and intermediate thickenings become indistinct, cell cavities to 8–12 µm long X 10 µm wide. Median cells oflobule to 1.75–3X longer than wide, cell cavities to 20 µm long X 10 µm wide, walls flexuose with indistinct trigones and small nodulose intermediate thickenings. Oil-bodies of the leaf lobe median cells: 2–3 (4) oil-bodies per cell, typically small, spherical 1–3 (4) µm in diam. or ovoid to ellipsoidal, to 2–4 µm X 1–3, lacking any significant ornamentation, often appearing as almost homogeneous oil droplets. The oil-bodies of the lobule and underleaf are similar to those encountered in the leaf lobe. Asexual reproduction;none known.
Monoicous, some plants cladautoicous with androecial branches a short distance below the inflorescence, otherwise androecial branches distant; one phenotype paroecious, the male bracts immediately below the female. Androecia bud-shaped to discoid, 2–4 (6) pairs of bracts, sessile or terminal on very short-stalked branches, occasionally some phenotypes returning to normal vegetative branch at the apex of the androecium. Gynoecia terminal on main or leading stem, some phases bearing 1 subfloral innovation of indeterminate length and subfloral branches 1–2 complete-leaf cycles below the gynoecia, other phases bearing 1–2 subfloral branches immediately below gynoecia. ♀ bracts and bracteoles in 1–2 (3) closely imbricate cycles. Innermost bract unequally bilobed; bract-lobe and lobule with acuminate apices and margins similarly dentate as those of the leaf-lobe, bract-lobule with 1–2 irregularly sized teeth at the base; innermost bracteole free from bracts, oblong in outline with subparallel margins, about ½ bilobed, the sinus narrowed, lobes lanceolate, acuminate at apex. Two archegonia per gynoecium. Perianth freely emergent, to 800 µm long X 400 µm wide, 3 major keels + 1–2 minor, supplementary, ventral keels; surface mammillose due to projecting and thickened tangential cell-walls, particularly the keels; perianth beak cylindrical and slightly expanding towards the mouth, beak to ca. 80–100 µm long, rim always terminated by dense, thick-walled, unicellular papillae, ca. 20 µm long; protuberances developing the entire length of the inner beaksurface.
Seta of 16–18 rows of epidermalcells and 6–8 rows of internal cells; elaters to (24) 26–30 per capsule; epidermal layer of 10–15 cells wide, thickenings at the angles of the epidermal cells not extending out as lobes, consequently the juxtaposed thickenings of 3-4 adjoining corners form a configuration with an evenly rounded or oval outline; internal layer with extensive, coarse, secondary deposits. Spores ± globose, to 45 µm at widest axis, interspersed with 8–10 rosettes; each rosette to 2.5 µm in diam., bearing a ring of ca. (6) 8–9 (10) conspicuous stelae; stelae never papillate, smooth, rarely branched, ca. 0.5–1.5× long as wide, to ca. 1–1.5 µm long × 0.75–1.25 µm wide at base, gradually tapering to an obtuse or rounded apex; spore wall papillae otherwise densely distributed between regions of the rosettes.
 However the gynoecia of the paroecious phenotype are on a lateral branches, where androecia would normally develop.
Affinities, differentiation & variation:
Frullania chevalieri along with the other three species of the section are the only species of the subgenus with a variously toothed leaf-lobe margin. Several other species of the genus, e.g., F. dentata Hatt. of subg. Trachycolea, also have toothed leaf-lobes. However, the four species of subg. Microfrullania sect. Microfrullania is immediately differentiated from those other taxa with toothed leaf-lobes by sharing: 1) the small plant size; 2) the strongly patent, cylindrical lobules; and 3) the subequally thickened cell walls of the leaf-lobe.
The delicately crenulate-denticulate or denticulate of Frullaniachevalieri immediately distinguishes it from F. microscopica, which has sharply and coarsely dentate margins with conspicuously spinose teeth. The monoicous habit and smooth leaf lobe surface of F. chevalieri apparently separate this species from F. parhami and F. neocaledonica. The latter two species are both supposedly dioicous and the intramarginal leaf-lobe cells are elevated, on their abaxial, free face, as a central, distinct thickened papilla. However, both F. parhami and F. neocaledonica remain only known from scant type material and require further investigation.
Because the oil-bodies, perianths, and sporophytes are only known from Frullaniachevalieri it is difficult to speculate on possible affinities. But, at least on the basis of the marginal dentition of the leaf-lobes, Frullaniachevalieri appears more closely allied to F. parhami and F. caledonica than F. microscopica, hence the decision to assign the latter species into its own subsection.
Geographic distribution: Frullaniachevalieri was previously only known from New Caledonia where it would appear to be locally common; Hattori (1977, 1984a, 1986a) listed many localities for a number of collections from that region. Frullaniachevalieri is a new record for New Zealand where it is restricted to the northern part of the North Island; it is currently known from collections from the Auckland District and appears to become increasing common northwards to Cape Reinga. The distribution of this species appears to be correlated with that of Agathisaustralis (kauri) forest, and it would be interesting to explore if the southern extent of Frullaniachevalieri correlates with that of this forest type.