The liverwort genera (Bryophyta: Hepaticae and Anthocerotae) of Britain and Ireland
Gametophyte. Plants minute, yellowish green leafy. The branching of the Lejeunea type. The stems with cortical cells clearly differentiated from the cells of the central strand (sections showing 7 cortical cells surrounding 3–4 central cells). Acrogynous. The leaf cells with trigones (small), or without trigones. Rhizoids present (scarce); short.
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; with the rounded keel crenulate from projecting cells, incubous; deeply, unequally bilobed (the dorsal lobes obliquely ovate, subfalcate and convex with the margin 2–4 crenulate or spinose-toothed and a deflexed, more or less acute apex; the ventral lobes about half the size, inflated, the apex comprising a unicellular tooth having a hyaline papilla at the base inside and a strongly inrolled free margin); complicate-bilobed. The ventral lobes much smaller than the dorsal ones; without a stylus. Underleaves smaller than the laterals though well developed and conspicuous (much shorter, distant, obdeltoid, considerably wider than the stems, about 2/3 bilobed, the lobes 2 cells wide at the base, widely diverging, acuminate, with 2-celled uniseriate tips); bilobed. The lobes widely divergent; acuminate, only two cells wide at the bases. The cells of the gametophyte with numerous small chloroplasts. The chloroplast-containing cells with conspicuous oil bodies (compound, 4–9 per cell). Gemmae absent (propagating vegetatively via deciduous dwarf branches with small, deformed leaves and underleaves).
The plants dioecious.
Male inflorescences terminating long branches, with 3–4 pairs of imbricate, ventricose, almost equally acutely or apiculately bilobed bracts, the antical one slightly dentate. Male bracts subtending a single antheridium. Female inflorescences on a short branch, usually with a single, simple subinvolucral innovation. Female bracts present (larger than the leaves, bilobed and more or less conduplicate, the acuminate lobes spinous-dentate, the postical one narrower). Bracteole present (about 1/3 bilobed, the lobes spinose-dentate, connate with at least one of the bracts). Perianth present; pyriform and shortly beaked, distally 5-keel-winged, the wings irregularly spinose. Perianth distally plicate. Perianth distally 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. 1 species (D. hamatifolia); England, Wales, Scotland, and Ireland.
Classification. Class/Division Hepaticae. Subclass/Class Jungermanniidae. Order Jungermanniales. Family Lejeuneaceae.
Illustrations. • D. hamatifolia: Jameson, in Macvicar (1926). • D. hamatifolia fig. IX (as Lejeunea): Pearson (1902). • D. hamatifolia: Pearson fig. IX 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’.