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

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L. Watson and M. J. Dallwitz

Lejeunea Libert corr. Hampe

Including Microlejeunea Steph.

Gametophyte. Plants minute to medium sized, yellowish to green, occasionally brown-tinged, leafy. The branching of the Lejeunea type. The stems with cortical cells clearly differentiated from the cells of the central strand (the sstems in T.S. exhibiting 5–25 central cells surrounded by 7 cortical cells). Acrogynous. The leaf cells with trigones (these small?), or without trigones; smooth, not mamillose.

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; overlapping to distant; spreading laterally, incubous; bilobed (the apex of the dorsal lobe blunt or rounded, the the ventral lobe small or sometimes vestigial, usually inflated, but not modified into a beaked sac, the apex comprising a blunt unicellular tooth); complicate-bilobed. The ventral lobes much smaller than the dorsal ones. The vegetative leaves without vittae. Underleaves smaller than the laterals though well developed and conspicuous (seldom more than half as big as the leaves, 1–4 times the width of the stem, more or less orbicular, bilobed to 1/3 or more, the lobes not divergent); bilobed. The lobes not divergent. The cells of the gametophyte with numerous small chloroplasts. Gemmae absent (and lacking other vegetative propagules).

The plants dioecious, or bisexual; when bisexual, having the gametangia grouped into bracteate inflorescences; autoecious.

Male inflorescences on short branches, the imbricate, more or less symmetrically bilobed bracts saccate, with bracteoles confined to the base of the inflorescence. Female inflorescences variousl terminating main axes, long or short branches, rarely on dwarf branches, often becoming pseudo-lateral by sub-involucral innovation. Female bracts present (more or less similar to the leaves, unequally bilobed). Bracteole present (bilobed, basally joined to one or both bracts). Perianth present; usually 5-keeled and often keel-winged, at least distally; not beaked.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. 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. 8 species; England, Wales, Scotland, and Ireland.

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

Illustrations. • L. cavifolia: Jameson, in Macvicar (1926). • L. cavifolia (as L. serpyllifoia): Pearson fig. X (1902). • L. cavifolia: Pearson fig. X, legend. • L. flava: Jameson, in Macvicar (1926). • L. flava: Pearson fig. XII (1902). • L. flava: Pearson fig. XII, legend. • cf. L. hibernica (as diversiloba): Jameson, in Macvicar (1926). • cf. L. hibernica (as diversiloba): Pearson fig. XV (1902). • cf. L. hibernica: Pearson fig. XV, legend. • L. holtii: Jameson, in Macvicar (1926). • L. holtii: Pearson fig. XIII (1902). • L. holtii: Pearson fig. XIII., legend. • L. mandonii (as macvicari): Jameson, in Macvicar (1926). • L. patens: Jameson, in Macvicar (1926). • L. patens: Pearson fig. XI (1902). • L. patens: Pearson fig. XI legend. • L. ulicina (as Microlejeunea): Jameson, in Macvicar (1926). • L.ulicina: Pearson fig. XIV (1902). • L. ulicina: Pearson fig. XIV, 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.’.