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

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L. Watson and M. J. Dallwitz

Pallavicinia S.F. Gray

Gametophyte. Plants thalloid, not leafy (with a thick midrib and flat or undulate, unistratose wings). Anacrogynous. Rhizoids pale brown; of one kind, all smooth.

The cells of the gametophyte with numerous small chloroplasts. The thallus simple, or pinnately branching; with a conspicuous median conducting strand (visible as a dark line); without ventral scales. Gemmae absent (?). The thallus without dorsal pores; without cavities.

The plants dioecious; with no grouping of gametangia into bracteate inflorescences. The antheridia biseriate, on either side of the midrib, protected by bracts (in the form of forwardly directed, laciniate scales).

The gametangia and capsules borne externally. The archegonia and sporophytes with a pseudoperianth (the archegonia on the dorsal surface of the thallus or on ventral branchs, in groups surrounded by an involucre of laciniate scales). Calyptra present and well developed (more or less protruding beyond the pseudoperianth).

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule long-pedicellate, shortly cylindrical. The capsule wall 2 layered. The capsule dehiscing via two valves, or dehiscing by four valves. Elaters present (long and narrow, scarcely attenuate, pale brown); bispirally thickened to thickend via 3–4 spirals; free to persistent on elaterophores. The elaterophores rudimentary or absent.

British representation. 1 species (P.lyellii); England, Wales, and Ireland.

Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Metzgeriales. Family Pallaviciniaceae.

Illustrations. • P. lyellii: Jameson, in Macvicar (1926). • P. lyellii: Pearson fig. 191 (1902). • P. lyellii: Pearson fig. 191 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.’.