| | The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland |
Gametophyte. Plants medium sized, green, reddish to reddish-brown or purplish black, leafy. With ascending branches usually arising ventrally, sometimes attenuated or gemmiferous, the male and female inflorescences on dwarf ventral branches. The stems with cortical cells clearly differentiated from the cells of the central strand, or with no clear differentiation of cortical and central tissues; not translucent (opaque). Plants often with flagella or flagelliform shoots or branches (these green, arising ventrally), or with neither flagella nor flagelliform shoots or branches. Acrogynous. The leaf cells thick walled, with trigones (these often large and bulging), or without trigones. Rhizoids present (but sometimes scarce except on the flagella); colourless.
The leafy shoots dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves, or dorsiventral, with the two ranks of laterals more or less equal in size and the ventral rank lacking. The vegetative leaves mostly sub-orbicular to ovate,only slightly asymmetrical to more or less symmetrical. The vegetative leaves not wedge-shaped; obliquely inserted; alternate; overlapping; succubous. The leaf margins entire; often dorsally incurved or inflexed; not or only slightly dorsally decurrent. The vegetative leaves orbicular, undivided (entire, apically broadly rounded to truncate or retuse); leaves not keeled; without vittae. Underleaves smaller than the laterals though well developed and conspicuous, or present but much reduced or vestigial (small except on gemmiferous shoots, often with slime papillae); bilobed (sometime, on gemmiferous shoots), or not bilobed. The cells of the gametophyte with numerous small chloroplasts. The chloroplast-containing cells with conspicuous oil bodies (mostly 2–3 per cell). Gemmae often common (on the margins of sometimes malformed lateral leaves or underleaves, sometimes associated with attenuated shoots), or rare to absent; 1–2 celled.
The plants dioecious; having the gametangia grouped into bracteate inflorescences.
Male inflorescences on dwarf ventral branches, spicate with bilobed bracts much smaller than the leaves. Male bracts subtending a single antheridium. Female inflorescences on dwarf ventral branches. Marsupia absent. Female bracts present (increasing in size acropetally). Female bracts similar in size to the (upper) leaves to larger than the (upper) leaves (the uppermost bilobed and larger than the leaves). Bracteole present (similar to the bracts). Perianth present; long exserted, trigonous above, the mouth entire to ciliate. Perianth distally smooth, not plicate. Perianth not beaked. Calyptra present and well developed (thin).
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule ovoid. The capsule wall 2 layered, or 3 layered. The spores unicellular when shed. Elaters present; bispirally thickened; free.
British representation. 4 species; England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Jungermanniales. Family Cephaloziaceae.
Illustrations. • O. denudatum: Jameson, in Macvicar (1926). • O. denudatum (as Cephalozia): Pearson fig. LXVI (1902). • O. denudatum (as Cephalozia): Pearson fig. LXVI legend. • O. elongatum: Jameson, in Macvicar (1926). • O. macounii: Jameson, in Macvicar (1926). • O. sphagni: Jameson, in Macvicar (1926). • O. sphagni (as Cephalozia): Pearson fig. LXV (1902). • O. sphagni (as Cephalozia): Pearson fig. LXV legend.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
