The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants thalloid, not leafy (with the ill-defined, broad midrib grading into unistratose, lobed wings, the margins scalloped into leaflike lobes). Dorsal, naked, anacrogynous. The leaf cells without trigones. Rhizoids restricted to the midrib, colourless; of one kind, all smooth.
The cells of the gametophyte with numerous small chloroplasts. The thallus several times branching dichotomously; without a conspicuous conducting strand (the midrib ill defined, often with a dorsal white line of calcium carbonate); with ventral scales (with a row on either side of the midrib). Gemmae often common (of two kinds). The thallus commonly with gemma-receptacles on the surface. The gemma receptacles usually present on the dorsal surface near the apex, flask- or cup-shaped with frilled margins. Gemmae stellate and more or less unistratose often present dorsally near the apex, and a stalked, slightly flattened, rounded to elliptical form in the receptacles. The thallus with inconspicuous dorsal pores; without cavities (with Nostoc-filled auricles visible as dark spots near the bases of the lobes).
The plants dioecious (male plants smaller than females); with no grouping of gametangia into bracteate inflorescences. The antheridia not protected by bracts (solitary, in dorsal cavities).
The archegonia and sporophytes not protected by bracts (at first naked, borne dorsally behind the apex, one of them after fertilization becoming immersed and covered by the pseudoperianth). The archegonia and sporophytes with a pseudoperianth (fusiform with the mouth constricted). Calyptra present and well developed (free, membranous, concealed within the pseudoperianth).
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule rather longly pedicellate, enclosed by the decumbent pseudoperianth, narrowly ovoid. The capsule wall 3–4 layered. The capsule with a basal collar, dehiscing by four valves (or rarely 6). The spores unicellular when shed. Elaters present; bispirally thickened; persistent on elaterophores. The elaterophores rudimentary, basal.
British representation. 1 species (B. pusilla); England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Metzgeriales. Family Blasiaceae.
Illustrations. • B. pusilla: Jameson, in Macvicar (1926). • B. pusilla: Pearson fig. CXCVI (1902). • B. pusilla: Pearson fig. CXCVI 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’.