The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland

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L. Watson and M. J. Dallwitz

Tritomaria Schiffn. ex Loeske

~ Sphenolobus, Lophozia. Including Saccobasis.

Gametophyte. Plants represented by patches, tufts or scattered shoots, leafy. The shoots prostrate to ascending, simple or furcate, often innovating under the female inflorescences. Acrogynous. The leaf cells usually large, with trigones (often bulging), or without trigones. Rhizoids colourless, or brown.

The leafy shoots dorsiventral, with the two ranks of laterals more or less equal in size and the ventral rank lacking. The vegetative leaves mostly markedly asymmetrical (with the postical margin arched and much larger than the antical, but less so in T. polita). The vegetative leaves transversely inserted, or sub-transversely inserted, the dorsal half more or less transverse, the ventral half oblique (the insertion transverse or with the ventral part oblique, sometimes broadly V-shaped); alternate; overlapping to distant; succubous. The leaf margins entire. The vegetative leaves usually several-lobed (2–3 -lobed, with the ventral one larger than the dorsal ones and the ventral margin without cilia, or if more or less symmetrical, lobed to only about 1/8); not complicate-bilobed; without vittae. The cells of the gametophyte with numerous small chloroplasts. Gemmae common to rare, or absent (usually present, 2-celled, at the apices of upper leaves).

The plants dioecious; having the gametangia grouped into bracteate inflorescences.

Male inflorescences terminal, with bracts in several pairs, similar to the leaves but saccate. Male bracts subtending a single antheridium, or 2 antheridia (these shortly pedicellate, ovoid-globose). Female inflorescences inadequately described - always terminal?. Female bracts present (2–5 lobed). Perianth present; the mouth contracted or not and entire or toothed. Perianth distally plicate.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. Elaters by generalization from Lophozia sensu lato, probably present (not mentioned by authorities consulted); if present, probably bispirally thickened; free.

British representation. 4 species; England, Wales, Scotland, and Ireland.

Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Jungermanniales. Family Lophoziaceae.

Comments. Unconvincingly separable from Barbilophozia (q.v.) via the descriptive data compiled here, exemplifying unsatisfactory, sensu stricto generic circumscriptions accepted by Smith in the Lophoziaceae. Illustrations. • T. exsectiformis (as Sphenolobus): Jameson, in Macvicar (1926). • T. exsecta (as Sphenolobus): Jameson, in Macvicar (1926). • T. exsecta (as Jungermsnia exsecta Schmid.): Pearson fig. CXLV (1902). • T. exsecta (as Jungermsnia exsecta Schmid.): Pearson fig. CXLV legend. • T. polita (as Sphenolobus): Jameson, in Macvicar (1926). • T. quinquedentata (as Lophozia): Jameson, in Macvicar (1926). • T. quinquedentata (as Jungermania lyoni): Pearson fig. CXLVI (1902). • T. quinquedentata (as Jungermania lyoni): Pearson fig. CXLVI legend.

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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.’.