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

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L. Watson and M. J. Dallwitz

Acrobolbus Nees in Gottsche et al.

Gametophyte. Plants pale yellowish green, leafy. Shoots prostrate, markedly dorsiventral, sparingly branched from the postical leaf angles, sometimes with stolons. Plants with flagella or flagelliform shoots or branches, or with neither flagella nor flagelliform shoots or branches. Acrogynous. The leaf cells thin walled, with trigones. Rhizoids present (scattered on the fertile stems); long and numerous colourless; of one kind, all smooth.

The leafy shoots in A. wilsonii 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; alternate; oblong-obovate, asymmetrical with antical margins nearly straight and shortly decurrent, the postical margins arched, spreading horizontally save below the female inflorescences, the margins entire, succubous; usually unequally 1/3–2/3 bilobed (the sinus acute, the lobes acuminate with the postical one usually larger); without vittae. The cells of the gametophyte with numerous small chloroplasts. Gemmae absent.

The plants dioecious.

Male inflorescences terminal becoming intercalary, with 4–10 concave appressed bracts smaller than the leaves. Female inflorescences terminal. Perigynium present and well developed (marsupial). Marsupia present as downgrowths from stem apices, surrounding the developing sporophytes and carrying them into the substrate (ovate-globose, developing after fertilization at right angles to the main axis, so that the shoot becomes bilaterally symmetrical). Female bracts present (the outer ones much larger than the leaves, unequally bilobed with acuminate lobes, coarsely spinose-dentate, amplexicaul-cordate). Perianth present. Calyptra present and well developed (adnate to the inner wall of the marsupium).

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem (the seta many cells in diameter). The capsule ovoid (the seta short bulbous-based). The capsule wall 5–10 layered. The capsule dark brown, not green. The spores unicellular when shed. Elaters present; bispirally thickened; free.

British representation. 1 species (A. wilsonii); Scotland and Ireland.

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

Illustrations. • A. wilsonii: Jameson, in Macvicar (1926). • A. wilsonii: Pearson fig. CLXXXI (1902). • A. wilsonii: Pearson fig. CLXXXI 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.’.