Flora of New Zealand Series

Dichiton Mont., Syll. Gen. Sp. Crypt. 52. 1856, nom. rej.

Cephalozia subg. Cephaloziella Spruce, Cephalozia 23, 62. 1882. Cephaloziella (Spruce) Schiffn. in Engler & Prantl, Nat. Pflanzenfam. 1(3): 98. 1893.

Cephalozia subg. Prionolobus Spruce, Trans. & Proc. Bot. Soc. Edinburgh 15: 508. 1885. Prionolobus (Spruce) Schiffn. in Engler & Prantl, Nat. Pflanzenfam. 1(3): 98. 1893.

Lophoziella Douin & Schiffn. in Douin, Rev. Bryol. 40: 67. 1913.

Evansia Douin & Schiffn. in Douin, Rev. Bryol. 40: 66. 1913; Douin, Bull. Soc. Bot. France 60: 480, 492. 1914 (1913).

Protocephaloziella Douin, Mém. Soc. Bot. France 29: 52, 55. 1920.

Type: Cephaloziella divaricata (Sm.) Schiffn. (≡Jungermannia divaricata Sm.)

Plants straggly, creeping, often as isolated plants amidst coarser bryophytes, sometimes in short tufts, usually deep green to often reddish to brownish to purplish red, in extreme cases piceous or blackish, very small to minute, usually under 350 µm wide with leaves, the leafy shoots sometimes becoming filiform and microphyllous, the plants without a system of basal, leafless axes. Branching sparing, irregular, the branches of lateral- and/or ventral-intercalary type, the branches often elongating indefinitely (if not terminated by a gynoecium); Frullania -type branches sometimes present in primitive taxa, Acromastigum -type branches very rare. Stems filiform, often sinuous or tortuous, ± wiry, the cortical cells ± firm, not hyaline, like the medullary cells or somewhat thicker-walled, occasionally a little larger. Leaves usually vertical, generally remote (the stems extensively exposed), uniformly bifid to 0.5–0.8, the insertion and orientation transverse (in ours) or in a few taxa succubous, the insertion lines extending to stem midline dorsally, the leaves often loosely folded; lobes ± divergent (when flattened), subequal to equal (rarely with dorsal lobe reduced), mostly narrowly acute to lanceolate, usually only (2)3–9(11) cells wide at base, entire or sometimes toothed, the abaxial surface smooth or in a few species with cellular outgrowths. Cells thin- to more often evenly thick-walled, sometimes strongly so, mostly subquadrate to short-rectangular, small, usually 8–15 µm wide (rarely larger), becoming somewhat larger toward the base; surface smooth to conspicuously papillose. Oil-bodies usually (2)3–9 per cell, finely and obscurely granular and usually appearing almost homogeneous, small, spherical to ovoid. Underleaves small (to 0.35 area of leaves), variable in size and form: lanceolate, as broad as stem and shallowly bilobed, to reduced, few-celled, triangular lamellae to vestigial and consisting of a slime papilla. Gemmae frequent in almost all species, from margins of uppermost malformed and often reduced leaves (and underleaves) which are dentate-margined, the gemmae 2-celled, elliptical, smooth or sometimes covered with papillae, or angulate.

Dioecious, autoecious or paroecious. Gametangia mostly on elongated leafy shoots, but sometimes ♂ or ♀ (or both) on reduced, few-leaved or leafless intercalary branches. Androe-cia usually similar in diameter to vegetative sectors or broader, loosely to compactly spicate (in non-paroecious taxa); bracts bilobed, like the leaves except ventricose at base and often more toothed; antheridia usually single per bract, the body ovoid, with cells in 4 irregular tiers, the stalk usually 1-seriate, very rarely 2-seriate. Gynoecia if unfertilized, always innovate, the innovations often indeterminate in length, the gynoecia with bracts and bracteoles in 2–3 series, those of innermost series connate (often strongly) and forming a cup- or urn-like sheath around perianth base (free only in a few species in subg. Schizophyllum); bracts similar to leaves except larger and with margins usually dentate (even when vegetative leaves are entire), usually 2-, less often 3-lobed; bracteole unlobed or bilobed, from ca. 0.5× to ca. subequal to bract in size. Perianth usually long-emergent, often ± prismatic, (3)4–5-plicate, somewhat but not greatly contracted to the truncate mouth; mouth often bleached, with cells variously elongated, mostly narrow, thick-walled and entirely or variously in part laterally free, lending the mouth mostly crenulate or, less often, ciliolate (but never long-ciliate).

Seta with 4(5–6) rows of large, swollen outer cells and 4 opposed rows of minute inner cells. Capsule long-exserted, ellipsoidal, the valves thin, 2-stratose; outer layer of cells with a one-phase ontogeny, all or most longitudinal and many transverse walls with well-defined nodular thickenings, the valve base with 4–5 large, swollen cells; inner layer of cells very similar, with similar, often weaker nodular thickenings, sometimes tangentially extended as incomplete to complete bands.

Spores small, 6–12 µm in diam., finely papillose, appearing nearly smooth; spore:elater diam. ratio mostly ca. 1:1. Elaters 2-spiral.

“Perhaps no genus of Hepaticae is more difficult than Cephaloziella ” (Schuster, 1980b, p. 39), with the consequence that it is poorly known taxonomically. The genus includes ca. 90 validly described species and is worldwide in distribution, including presence in both the Arctic (north to ca. 83° N) and the Antarctic. Many of the species were recognized by Douin (e.g., Douin, 1920) in his detailed study of the genus. His studies, however, are of limited use in our understanding of the genus, since his concepts are overly precise, unrealistic and noncritical. Müller (1947, 1951–58) and Schuster (1972a, 1980b, 1996a, 2002a) did much to advance our knowledge of the taxonomy of the group.

The genus is fairly well represented in the Antipodes. The southern South American species are treated in Fulford (1976), but her treatment is of limited value since it is neither complete nor critical. Engel (1978) included three species for the Brunswick Peninsula (Strait of Magellan) (Cephaloziella dusenii Steph., C. gemmata J.J.Engel and C. verrucosa Steph.), and Engel (1990a) recorded one species, C. dusenii, for the Falkland Islands. Arnell (1963) treated 12 South African taxa, and Bednarek-Ochyra et al. (2000) treated two species, C. hispidissima and C. varians for Antarctica. The genus is subdivided into five subgenera and several sections (Schuster 1980b, 1996a). The 17 species present in New Zealand belong to four subgenera: 13 occur in subg. Cephaloziella, one in  subg. Schizophyllum, one in  subg. Evansia, and one in subg. Distochopsis. One species, C. rufobrunnea R.M.Schust., is of questionable affinity, even generically, and is not assigned to a subgenus.

Several inherent aspects of the genus make them the most difficult and technical of New Zealand hepatics. They are small to minute in size, frequently sterile, often present either in small quantity or as isolated strands amidst other bryophytes, frequently intimately admixed with another taxon of Cephaloziella, and have subtle characters that at times offer difficulties. For example, sexuality is often difficult to determine, even when ♂ and ♀ gametangia are present. Plants are either obviously dioecious (the ♂ and ♀ plants not or only casually admixed), “pseudodioecious” (autoecious, but ♂ and ♀ on long, leafy axes, often so widely separated that connections between the two often decay and plants seem dioecious); or obviously autoecious (♂ and ♀ branches closely associated and juxtaposed, in ours the ♀ often on short branches arising from near the androecial axis) or paroecious. For a detailed account of the methodology and taxonomic problems in the genus, see the treatment of North American taxa in Schuster (1980b).

The treatment below is drawn heavily from Schuster (1972a, 1996a).

References: Douin (1920); Schuster (1972a, 1980b, 1996a, 2002a).

Because the genus is the most difficult and technical of our hepatics, a key to subgenera, after Schuster (2002a), is provided.