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

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L. Watson and M. J. Dallwitz

Adelanthus Mitt.

Gametophyte. Plants leafy. With erect shoots arising from creeping rhizomatous stems, and dwarf, ventral fertile branches usually associated with the bases of shoots, but seemingly unknown in Britain. The stems with cortical cells clearly differentiated from the cells of the central strand (these being thick walled and opaque in optical section). Plants with flagella or flagelliform shoots or branches (from lower parts of the stems). Acrogynous. The leaf cells with trigones, or without trigones. Rhizoids mostly confined to the lower parts of the stems and on the flagella, colourless; of one kind, all smooth.

The leafy shoots 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 very obliquely inserted; alternate; horizontal or patent, oval to rounded and often toothed, ventrally secund, the dorsal margin inflexed, distant on the sterile stems, on the fertile stems sub-imbricate and succubous. The leaf margins toothed; dorsally incurved or inflexed; dorsally decurrent. The vegetative leaves undivided; without vittae. Underleaves present but much reduced or vestigial, or absent. The cells of the gametophyte with numerous small chloroplasts.

The plants dioecious.

The archegonia and sporophytes pseudo-involucrate, via 2–4 opposite, scale-like leaves. Male inflorescences comprising dwarf ventral branches, mostly near the bases of shoots, the bracts scale-like. Male bracts subtending a single antheridium. The antheridial stalks 1 seriate. Female inflorescences comprising dwarf ventral branches, mostly near the bases of shoots. Female bracts present (the kinnermost smaller than the leaves, tristichous). Perianth present; pyriform, ovoid or fusoid, its mouth connivent, dentate, obliquely truncate and split. Calyptra present and well developed (fleshy, bearing he sterile archegonia).

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem (the seta massive, many small cells in diameter). The capsule globose to ovoid. The capsule wall fleshy, 5–7 layered. The capsule leathery, dehiscing by four valves. Elaters present; free.

British representation. 2 species; England, Wales, Scotland, and Ireland.

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

Illustrations. • A. decipiens: Jameson, in Macvicar (1926). • A. decipiens: Pearson fig. LXXIX (1902). • A. decipiens: Pearson fig. LXXIX legend. • A. dugortiensis: Jameson, in Macvicar (1926).

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.’.