The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants thalloid, not leafy (parchment-like when dry, the dorsal surface not reticulate). Anacrogynous (in that the 1–2 cm-stalked female receptacles arise behind the thallus apices). Rhizoids of two kinds, smooth and tuberculate.
The cells of the gametophyte with numerous small chloroplasts. The thallus branching dichotomously; opaque, without a conspicuous conducting strand; with ventral scales (one row on either side of the midrib, purple, obliquely semi-lunar and initially with two elongated appendages); without gemma-receptacles; with conspicuous dorsal pores. The pores scarcely elevated, simple. The thallus containing conspicuous cavities. The air chambers in several layers in section. The ventral surface deep purple to purplish black.
The plants dioecious, or bisexual (then monoecious). The antheridia not protected by bracts.
The gametangia and capsules borne externally. The archegonia and sporophytes not protected by bracts. The archegonia and sporophytes without a pseudoperianth. The gametangia borne on special receptacles. The female receptacles arising behind the thallus apex, stalked (the stalk 1–2 cm long); with 4–7 rounded lobes. The male receptacles on the dorsal surface of the midrib, sessile.
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule not dehiscing via a lid ... The spores unicellular when shed. Elaters present; bispirally thickened; free.
British representation. 1 species (R. hemisphaerica); England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Marchantiidae. Order Marchantiales. Family Aytoniaceae.
Illustrations. • R. hemisphaerica: Jameson, in Macvicar (1926). • R. hemisphaerica: Pearson fig. CCX (1902). • R. hemisphaerica: Pearson fig. CCX 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’.