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

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L. Watson and M. J. Dallwitz

Anastrepta (Lindb.) Schiffn.

Gametophyte. Plants forming reddish-brown to brown or green, lax tufts, or scattered shoots among other plants, leafy. The stems tall, erect, mostly simple, branches mostly proceeding from the postical angles of leaves below female inflorescences. Acrogynous. The leaf cells with trigones. Rhizoids present; numerous only on lower parts, short, colourless; of one kind, all smooth.

The leafy shoots stem-clasping, dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves to dorsiventral, with the two ranks of laterals more or less equal in size and the ventral rank lacking. The vegetative leaves markedly asymmetrical. The vegetative leaves very obliquely inserted (the bases stem-clasping, semi-amplexicaul with their dorsal margins interdigitating); alternate; overlapping (imbricate); spreading, succubous. The leaf margins toothed (the antical margin sometimes with a basal tooth), or entire; deflexed (antically slightly, postically broadly); dorsally decurrent. The vegetative leaves obliquely ovate-cordate, basally concave, bilobed (with the broad, shallow sinus forming two short, wide, acute to blunt lobes); not complicate-bilobed. The ventral lobes similar in size to the dorsal ones. The vegetative leaves without vittae. Underleaves present but much reduced or vestigial, or absent (if present, very small and subulate); not bilobed. The cells of the gametophyte with numerous small chloroplasts. Gemmae rare (at the apices of leaf lobes, reddish-brown).

The plants dioecious.

Male inflorescences intercalary, comprising 3–5 pairs of leaflike, imbricate, shortly bidentate, saccate bracts with a tooth at the base of the antical margin, smaller than the leaves. Male bracts subtending a single antheridium, or 2 antheridia (shortly pedicellate). Female bracts present (shallowly several-lobed, often toothed). Perianth present (rarely); obovoid, and contracted to the dentate mouth. Perianth distally plicate.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule wall 5 layered. The spores unicellular when shed. Elaters present; reddish brown, bispirally thickened; free.

British representation. 1 species (A. orcadensis); England, Wales, Scotland, and Ireland.

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

Illustrations. • A. orcadensis: Jameson, in Macvicar (1926). • A. orcadensis (as Jungermania): Pearson fig. CLV (1902). • A. orcadensis (as Jungermania): Pearson fig. CLV 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.’.