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

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L. Watson and M. J. Dallwitz

Hygrobiella Spruce

Gametophyte. Plants slender, in dull green to greenish- or reddish-brown patches or tufts mixed with other bryophytes, leafy. The stems procumbent to erect, the few branches lateral. The stems with cortical cells clearly differentiated from the cells of the central strand (the cortical cells large and hyaline, those of the central strand small and relatively thicker walled). Plants with flagella or flagelliform shoots or branches (these microphyllous or leafless, sometimes constituting the entire plants). Acrogynous. The leaf cells without trigones. Rhizoids present (but very scarce, at stem bases and on flagella), or absent.

The leafy shoots more or less dorsiventral, the three-ranked leaves more more less equal in size. The vegetative leaves transversely inserted (conduplicate-concave, oval to oval-lanceolate); alternate; (sub-) overlapping. The leaf margins entire; incurved or inflexed (at least, the leaves concave); not or only slightly dorsally decurrent. The vegetative leaves minute on the lower parts of the stems and branches, larger distally, bilobed (to about a third); without vittae. Underleaves similar in size to the laterals to smaller than the laterals though well developed and conspicuous (resembling them or rather smaller and more triangular, occasionally entire). The cells of the gametophyte with numerous small chloroplasts. Gemmae absent.

The plants dioecious.

Male inflorescences terminal before becoming intercalary, the bracts similar to the upper leaves but basally more concave. Male bracts subtending a single antheridium. Female inflorescences terminating stems and branches, often with innovations. Female bracts present (one to three pairs surrounding the perianth, resembling the leaves but longer, 1/5–1/4 bilobed). Bracteole present (resembling the bracts, or sometimes entire). Perianth present; fusiform, composed of two cell layers to above the middle, distally trigonous, the mouth ciliate-dentate and almost closed. Calyptra membranous, whitish.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule globose; brown, not green. Elaters present; bispirally thickened; free.

British representation. 1 species (H. laxifolia); England, Wales, and Scotland.

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

Illustrations. • H. laxifolia: Jameson, in Macvicar (1926). • H. laxifolia: Pearson fig. LXXVII (1902). • H. laxifolia: Pearson fig. LXXVII 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.’.