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

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L. Watson and M. J. Dallwitz

Ptilidium Nees

Gametophyte. Plants generally densely tufted, usually reddish brown or brown, rarely olive green, leafy (the leaves usually becoming seconsarily pigmented). The branching of the Frullania type. The stems with cortical cells clearly differentiated from the cells of the central strand (the cotical cells thick walled and soon becoming pigmented, the medullary cell walls thin and hyaline). Plants with neither flagella nor flagelliform shoots or branches; without paraphyllia. Acrogynous. The leaf cells with trigones (usually, large). Rhizoids present (usually few and short).

The leafy shoots dorsiventral, with two equal ranks of lateral leaves and a third, ventral rank of smaller underleaves. The vegetative leaves sub-orbicular, more or less transversely inserted to obliquely inserted (not conduplicate); alternate; overlapping; incubous. The leaf margins very multi-ciliate (all the margins normally with long cilia). The vegetative leaves bilobed, or several-lobed (the dorsal lobe larger than the ventral, but ostensibly 2–6 lobed by subdivision of the primary lobes, the margins with numerous uniseriate cilia, the ventral one with an internal water sac); without vittae. Underleaves smaller than the laterals though well developed and conspicuous (similar in shape but only about half as large). The cells of the gametophyte with numerous small chloroplasts. The chloroplast-containing cells with conspicuous oil bodies (these very small and numerous). Gemmae absent.

The plants dioecious.

Male inflorescences terminating main or lateral branches, becoming intercalary, with several pairs of closely imbricate, transverse, complicate-concave, ventricose, unequally 3–4 lobed bracts smaller than the leaves. Male bracts subtending a single antheridium, or 2 antheridia (these large). The antheridia not mixed with paraphyses. Female inflorescences terminal on the stem or main branches, but later on short laterals through innovations. Female bracts present (larger and more densely ciliate than the leaves and underleaves). Bracteole present (larger and more densely ciliate than the leaves and underleaves, cf. the bracts). Perianth present; cylindrical to obpyriform, and narrowed to the 4–5 lobed and ciliate mouth. Perianth distally plicate.

Sporophyte. The sporophyte elevated by elongation of the seta, with no intercalary meristem. The capsule globose to ovoid. The capsule wall 4–5 layered. The capsule dark brown, not green. The spores unicellular when shed. Elaters present; bispirally thickened; free.

British representation. 2 species; England, Wales, Scotland, and Ireland.

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

Illustrations. • P. ciliare: Jameson, in Macvicar (1926). • P. ciliare (as Blepharozia ciliaris): Pearson fig. XXXVIII (1902). • P. ciliare (as Blepharozia ciliaris): Pearson fig. XXXVIII legend. • P. pulcherrimum: Jameson, in Macvicar (1926). • P. pulcherrimum (as Blepharozia): Pearson (1902). • P. pulcherrimum (as Blepharozia): Pearson legend.

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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.’.