The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants thalloid, not leafy (forming extended deep green ptches or rosettes, the thallus flat or somewhat concave with sinuate-lobed margins the apices emarginate). Acrogynous (in that the 2–5 cm-stalked, rayed female receptacles are apical). Rhizoids of two kinds, smooth and tuberculate.
The cells of the gametophyte with numerous small chloroplasts. The thallus richly branching dichotomously; without a conspicuous conducting strand (but at least sometimes with a dark line associated with the midrib); with ventral scales (in two rows along the midrib, and two rows on either side, purple to colourless, sometimes projecting beyond the margins of the thallus); nearly always with gemma-receptacles on the surface. The gemma receptacles cup-shaped with frilled margins. Gemmae rotund-reniform, nearly flat, inserted vertically in groups at the bottom of the gemma cups. The thallus under the microscope with conspicuous dorsal pores. The pores complex (barrel-shaped, comprising four four-celled rings,superimposed so as to appear from above as two rings). The thallus containing conspicuous cavities. The air chambers in a single layer in section. The ventral surface pale green to reddish brown.
The plants dioecious.
The gametangia and capsules borne externally. The archegonia and sporophytes with a pseudoperianth. The gametangia borne on special receptacles. The female receptacles apical, stalked (stalks 2–5 cm); stellately about 9–11 rayed. The male receptacles apical, peltate, less common them females, stalked.
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule dehiscing irregularly. Elaters present; long and attenuate, yellow, bispirally thickened; free.
British representation. 1 species (M. polymorpha); England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Marchantiidae. Order Marchantiales. Family Marchantiaceae.
Illustrations. • M. polymorpha: Jameson, in Macvicar (1926). • M. polymorpha: Pearson fig. CCVIII (1902). • M. polymorpha: Pearson fig. CCVIII legend.
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’.