Calypogeiaceae Arnell
Calypogeiaceae Arnell in Holmberg, Skand. Fl. 2: 189. 1928.
Type: Calypogeia Raddi
Plants anisophyllous, closely prostrate and creeping, usually closely attached to substrate, dorsiventrally aplanate, pale to whitish green to yellow-green to (Mnioloma) brownish, medium-sized (to 1.8 mm wide in ours). Branching sparing and irregular, the branches predominantly of ventral-intercalary type; Frullania -type branches sparing to common in many taxa, or lacking (Mnioloma); Acromastigum - or Microlepidozia -type branches present in a few, exotic taxa; ventral-intercalary stolons absent or if present (Mnioloma), then rhizoidous, microphyllous and geotropic. Stem soft-textured, essentially undifferentiated, the cortex ill-defined, at most with 1 layer of ± firm-walled cells. Rhizoids from basal cells of most underleaves. Leaves laterally strongly and widely spreading, the insertion strongly incubous, nearly longitudinal, nearly straight but arched at the dorsal end and extending to stem midline or nearly so (at most with 2 rows of leaf-free cortical cells), the leaves usually ovate to ovate-triangular, infrequently ellipsoidal, broad-based, plane or slightly convex, undivided and usually entire (in some taxa bidentate), the margins entire. Cells (intramarginal) of leaves usually large, subisodiametric or feebly elongated at leaf bases, thin-walled, with trigones lacking, or, less often, small, rarely nodulose; surface smooth or sometimes weakly papillose. Oil-bodies 2–11(13) per cell, colorless to smokey grey to brownish grey, bluish in a few species, finely to coarsely botryoidal. Underleaves distinct, typically 0.2–0.4× area of lateral leaves, inserted on a ± acroscopically arched line, the apex bifid to feebly retuse and then with the lobes each reduced to a slime papilla; lamina margins at times with a strong lateral tooth on one or both sides; underleaves at base with a large, dense, small-celled, rhizoid-initial area, the rhizoid-initials at first forming prominent cushions. Asexual reproduction (Calypogeia) by 2-celled, pale green gemmae from malformed and reduced leaves of erect, gemmiparous, tapered shoot apices.
Autoecious (in ours) or, less commonly, dioecious. Androecia on short, ventral-intercalary branches (except Eocalypogeia spp.), small, spicate; bracts tiny, pouched; antheridia 1(2–3) per bract, the stalk 1- or 2-seriate. Gynoecia on very short, leafless, ventral-intercalary branches (except Eocalypogeia spp.) that are hidden at the time of archegonial maturation within underleaf axils; gynoecia producing at most 1–2 pairs of reduced bracts or bractlets; sporophyte protected by a conspicuous, pendulous, usually subterranean, densely rhizoidous marsupium (formed after fertilization), the unfertilized archegonia carried down within the marsupial canal; calyptra distinct; perianth lacking.
Seta with 18–20 rows of outer cells, similar in diameter or slightly larger than the many inner cells. Capsule long-ellipsoidal to cylindrical, the valves spirally twisted or not, 2-stratose; outer layer of cells with two-phase development: primary longitudinal and transverse walls lacking thickenings, the primary cells divided 1–3 times by secondary longitudinal walls with nodulose to sheet-like pigmented thickenings; inner layer of cells with numerous semiannular bands.
Spores granular. Elaters nearly straight, hardly tapered at the tips, bispiral.
A widespread family with four genera. Eocalypogeia (R.M.Schust.) R.M.Schust. has two species (Schuster, 1995c); E. quelpartensis (S.Hatt. & Inoue) R.M.Schust. is scattered east Asiatic in range (Japan, Korea, Thailand); E. schusterana (S.Hatt. & Mizut.) R.M.Schust. is disjunct in Arctic to boreal areas of North America and Asia and is found in Newfoundland, Nova Scotia, west Greenland, Alaska and Siberia (Schuster, 1969c, 1995c, 2000a, p. 489). Metacalypogeia (S.Hatt.) Inoue has two species (Schuster, 1995c), M. cordifolia (Steph.) Inoue and M. montana (Horik.) Inoue, both of Japan (see Inoue, 1959; see also Schuster, 1969c). Calypogeia and Mnioloma occur in New Zealand.
