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

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L. Watson and M. J. Dallwitz

Cololejeunea (Spruce) Schiffn.

Gametophyte. Plants minute and tender, leafy. The shoots procumbent or sometimes with ascending tips, irregularly sub-pinnately branched. The branching of the Lejeunea type (but the branches arising internally with a basal collar). The stems with cortical cells clearly differentiated from the cells of the central strand (with 5–6 cortical cells surrounding a single central one). Acrogynous. The leaf cells with trigones, or without trigones; conspicuously mamillose (commonly), or smooth, not mamillose. Rhizoids present (in clusters, seemingly replacing the underleaves).

The leafy shoots dorsiventral, with the two ranks of laterals more or less equal in size and the ventral rank lacking. The vegetative leaves very narrowly more or less transversely inserted (not dimorphic, often very conspicuously mamillose); alternate; overlapping, or distant; very unequally bilobed (the ventral lobe inflated, folded under the dorsal one and much smaller, the dorsal lobe apically rounded to more or less acute); complicate-bilobed. The ventral lobes much smaller than the dorsal ones; with a stylus (this persistent or caducous, unicellular or several celled and uniseriate). The cells of the gametophyte with numerous small chloroplasts. Gemmae absent.

The plants bisexual; having the gametangia grouped into bracteate inflorescences; autoecious.

Male inflorescences terminating long or short branches, the bracts having the ventral lobe more inflated then in the leaves. Male bracts subtending a single antheridium, or 2 antheridia. Female inflorescences terminal on long or short branches, often becoming pseudo-lateral via subinvolucral innovation. Female bracts present (smaller to larger than the leaves). Perianth present; free, obovoid to obpyriform, 5-keeled at least distally, and shortly beaked via the apex contricting into a tubular mouth; distally beaked. Calyptra present and well developed (free).

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule globose. The capsule wall 2 layered. The capsule dehiscing by four valves (for 2/3 of its length, the proximal third solid). The spores unicellular when shed. 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. 3 species; England, Wales, Scotland, and Ireland.

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

Illustrations. • C. calcarea: Jameson, in Macvicar (1926). • C. calcarea (as Lejeunea): Pearson fig. XVI (1902). • C. calcarea: Pearson fig. XVI, legend. • C. minutissima: Jameson, in Macvicar (1926). • C. minutissima (as Lejeunea): Pearson fig. XVIII (1902). • C. minutissima: Pearson fig. XVIII, legend. • C. rossettiana: Jameson, in Macvicar (1926). • C. rossettiana (as Lejeunea): Pearson fig. XVII (1902). • C. rossettiana: Pearson fig. XVII, 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.’.