The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants thin, pale- or yellowish green patches, or growing through other bryophytes, leafy. The shoots prostrate, very sparsely branched, the very short fertile branches arising ventrally. Acrogynous. The leaf cells thin walled, with trigones (small), or without trigones. Rhizoids present (arising in bunches from the bases of the underleaves, and also scattered along the stems); colourless.
The leafy shoots dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves. The vegetative leaves not wedge-shaped; very obliquely inserted; alternate; overlapping; more or less spreading horizontally, mostly flat, ovate-quadrate, antically slightly decurrent, succubous; 1/6–1/3 bilobed (the lobes acute, broadlt triangular and often somewhat unequal, the sinus acute to rounded). Underleaves smaller than the laterals though well developed and conspicuous (bilobed almost to their bases, sometimes basally connate with the leaves). The cells of the gametophyte with numerous small chloroplasts.
The plants bisexual; having the gametangia grouped into bracteate inflorescences; autoecious.
Male inflorescences arising ventrally, spicate, very short and hidden by the lateral leaves, with 4–8 pairs of bilobed bracts. Perigynium present and well developed (marsupial). Marsupia present as downgrowths from stem apices, surrounding the developing sporophytes and carrying them into the substrate (initially spherical, becoming cylidrical and rhizoidal at maturity). Female bracts present (small, at the apices of the female inflorescences). Perianth present. Calyptra present and well developed (shorter than the marsupium and connate with it for 2/3 of it length).
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule shortly cylindrical. The capsule wall 2 layered (the inner layer with semi-annular thickenings). The capsule dehiscing by four valves (to its base, the valves erect and straight). The spores unicellular when shed. Elaters present; bispirally thickened; free.
British representation. 1 species (G. graveolens); Scotland and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Jungermanniales. Family Geocalycaceae.
Illustrations. • G. graveolens: Jameson, in Macvicar (1926).
To view the illustrations with detailed captions, go to the interactive key. This also offers 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.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland. Version: 24th February 2016. delta-intkey.com’.