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| 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.
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’.
