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

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L. Watson and M. J. Dallwitz

Saccogyna Dum.

Gametophyte. Plants medium sized to robust, in pale olive- or brownish-green flat patches, sometimes extensive or creeping through other bryophytes leafy. The shoots procumbent, with occasional ventral branching including the dwarf male and female branches. Acrogynous. The leaf cells thin walled, with trigones (these small). Rhizoids present (tufted at the underleaf bases); colourless.

The leafy shoots dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves. The vegetative leaves very obliquely inserted; more or less opposite; overlapping (imbricate); sub-opposite, spreading horizontally, shortly decurrent, succubous; oblong, ovate-oblong or ovate-triangular, plane or convex, undivided (with rounded apices); without vittae. Underleaves smaller than the laterals though well developed and conspicuous (about as wide as the stems, triangular-acuminate with sharply toothed margins, often basally joined to one or both adjoining laterals). The cells of the gametophyte with numerous small chloroplasts. Gemmae absent.

The plants dioecious.

Male inflorescences on very small dwarf ventral branches concealed under lateral leaves, the 4–5 pairs of tiny, bilobed, basally saccate bract. Male bracts subtending a single antheridium, or 2 antheridia (these large). The antheridial stalks shortly 1 seriate. Female inflorescences comprising dwarf ventral branches. Perigynium present and well developed (marsupial). Marsupia present as downgrowths from stem apices, surrounding the developing sporophytes and carrying them into the substrate (this about 2 mm long at maturity, horizontal, cylindrical and rhizoid-covered). Female bracts present (i.e., with a few small bracts at the mouth of the marsupium). Perianth present.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem (the seta stout). The capsule shortly cylindrical. The capsule wall 2 layered (the inner wall with numerous, semi-annular thickenings). The capsule dehiscing by four valves (to the base). The spores unicellular when shed. Elaters present; reddish-brown, closely bispirally thickened; free.

British representation. 1 species (S. viticulosa); England, Wales, and Ireland.

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

Illustrations. • S. viticulosa: Jameson, in Macvicar (1926). • S. viticulosa: Pearson fig. CLXXXII (1902). • S. viticulosa: Pearson fig. CLXXXII 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.’.