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

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L. Watson and M. J. Dallwitz

Marchesinia S.F. Gray

Gametophyte. Plants relatively large, in olive- to blackish-green or rarely brownish, flat patches, leafy. The branching of the Frullania type, or of the Lejeunea type, or of the Frullania type and of the Lejeunea type. The stems with cortical cells clearly differentiated from the cells of the central strand (in T.S. exhibiting numerous central cells surronded by twelve or more cortical cells). Acrogynous. The leaf cells with trigones (small). Rhizoids present; short, colourless, or brown.

The leafy shoots dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves. The vegetative leaves with J-shaped insertion; alternate; somewhat to closely overlapping; spreading horizontally, the margins entire to slightly sinuous, incubous; bilobed (almost to the base, the dorsal lobe crossing the stem, ovate to broadly elliptical or sub-orbicular, slightly convex with a deflexed, rounded apex, the ventral lobe about half the size, ovate-oblong, inflated at the keel with two teeth near the base); complicate-bilobed; leaves keeled proximally to the lobes. The ventral lobes much smaller than the dorsal ones. The vegetative leaves without vittae. Underleaves much smaller than the laterals though well developed and conspicuous (about three times as broad as the stem, broadly orbicular, simple, flat, the margins sinuous, the apex straight to slightly emarginate); not bilobed. The cells of the gametophyte with numerous small chloroplasts. Gemmae absent.

The plants bisexual; having the gametangia grouped into bracteate inflorescences; autoecious.

Male inflorescences terminal and spicate on short branches, becoming intercalary and sometimes successive, the 3–6 pairs of bilobed bracts smaller than the leaves, the doral lobe larger than the ventral, both with rounded apices. Female inflorescences terminal on short branches. Female bracts present (slightly larger than the leaves, unequally bilobed with ovate, entire lobes, the ventral one about 2/3 as long as the dorsal). Bracteole present (oblong-cuneate, apically retuse). Perianth present; becoming exserted more than half its length, obcuneate, strongly compressed, shortly beaked, the mouth entire; distally beaked.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule globose. The capsule wall 2 layered (the inner wall fenestrated with 16 large pits). Elaters present; unispirally thickened; persistent on elaterophores (orientated vertically in the unopened capsules and extending to the floor, remaining attached by their upper ends to the inner walls of the distal ends of the dehiscing capsule valves and their trumpet-shaped lower ends becoming free).

British representation. 1 species (M. mackaii); England, Wales, Scotland, and Ireland.

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

Illustrations. • M. mackaii: Jameson, in Macvicar (1926). • M. mackaii (as Lejeunea): Pearson fig. VII (1902). • M. mackaii: Pearson fig. VII 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.’.