The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants small to robust, greenish to brownish but not reddish leafy. Without leafless rhizomes, the stems leafy throughout, prostrate with ascending apices, branching irregularly. Plants with neither flagella nor flagelliform shoots or branches. Acrogynous. The leaf cells thin walled, with trigones (but small), or without trigones. Rhizoids present (rather numerous, often more or less to the stem apices); fuscous.
The leafy shoots radially symmetrical, with three ranks of similar and more or less equal sized leaves to dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves. The vegetative leaves very obliquely inserted; alternate; overlapping to distant; more or less flat, sub-erect to spreading horizontally, ovate-oblong to rounded-quadrate, the antical margins not or only slightly decurrent, succubous. The leaf margins more or less toothed, or entire; flat to deflexed; not or only slightly dorsally decurrent. The vegetative leaves undivided, or several-lobed (entire, apically retuse or with 2–4 blunt teeth); without vittae. Underleaves present but much reduced or vestigial (small, filiform, limited to new growth). The cells of the gametophyte with numerous small chloroplasts.
The plants bisexual; having the gametangia grouped into bracteate inflorescences; autoecious.
Male inflorescences terminal becoming intercalary, on main and lateral branches, with 4–5 pairs of closely imbricate, erect, concave and basall saccate bracts smaller than the leaves, with a single tooth or small inflated lobe at the base of the antical margin. Male bracts subtending a single antheridium (usually, this globose-ovoid). Female inflorescences terminating branches. Female bracts present (similarly sized to the leaves or somewhat larger, with recurved margins, emarginate or toothed). Perianth present; shortly exserted, terminal on main or lateral branches, broadly obovate and slightly longer than wide, laterally compressed, the bilabiate mouth truncate, rounded and more or less crenulate to denticulate.
Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule ovoid; dark brown, not green. The spores unicellular when shed. Elaters present; darker brown than the spores, bispirally thickened; free.
British representation. 1 species (P. interruptum); England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Jungermanniales. Family Plagiochilaceae.
Illustrations. • P. interruptum: Jameson, in Macvicar (1926). • P. interruptum: Pearson fig. CXI (1902). • P. interruptum: Pearson fig. CXI 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. delta-intkey.com’.