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| The moss families (Bryophyta, Musci) of Britain and Ireland |
Flag-mosses.
Gametophyte. Tiny, almost stemless plants resembling minute buds on persistent protonemata, the leaves without chlorophyll. Acrocarpous; the male and female plants gregarious, or the plants scattered. Mature plants about 1–3 mm high. The leaves ovate to lanceolate; spiral; almost nerveless (sometimes with a faint vestigial nerve in the upper part only). Leaf blade apices pointed; not apiculate; apically acute. Leaf blade margins concave; distally bluntly dentate. The basal leaf cells longitudinally much elongated; hexagonal, or rhomboidal; smooth. The walls of basal leaf cells thin; straight. The angular cells not well differentiated. The mid-leaf cells longitudinally much elongated; hexagonal, or rhomboidal; smooth. The walls of the mid-leaf cells thin; straight.
Plants (pseudo-) dioecious (with male and female plants from the same, persistent protonema). Plants gemmiferous, or not gemmiferous; the gemmae when present, in leaf axils and or on rhizoids (rhizoidal).
Sporophyte. Capsules exserted; more or less horizontal, or inclined; symmetrical; (sub-) globose, or ellipsoid; without an externally conspicuous apophysis; with an annulus (this large). Calyptra symmetrical (becoming twisted); splitting down one side. Capsules with a peristome. The peristome single. The peristome teeth 16; not basally joined; not deeply cleft; perforated (in the sense of being divided below, but entire above); exteriorly with a fine longitudinal dividing line between the transverse bars. The operculum mamillate (and blunt). Setae slender, long, to 2.5 cm; straight (twisted when dry); pale red.
Ecology. In wet places, or mesophytic. On clayey banks of streams and ditches, and dried-up beds of ponds and reservoirs.
Cytology. Haploid chromosome number, n = 13.
Representation in Britain and Ireland. 1 species. Discelium (Flag-moss). Northern Scotland, southern Scotland, northern England, English Midlands, Wales, southeast England, central southern England, southwest England, and Ireland (generally rare, except in the Pennines where D. nudum is sometimes locally abundant).
Classification. Class Bryopsida; Subclass Funariideae; Order Funariales.
Illustrations. • Discelium nudum: Dixon. DISCELIACEAE: Discelium nudum (Dicks.) Brid.
From Dixon and Jameson (1924), the unscaled screen display approximately 2.5X the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. Discelium nudum. • Catoscopiaceae and Disceliaceae: Berkeley. DISCELIACEAE: 6, Discelium nudum (Dicks.) Brid.; a, habit; b, leaf; c, capsule; d, part of peristome, with annulus and spores. CATOSCOPIACEAE: 7, Catoscopium nigritum (Hedw.) Brid.; a, habit; b, leaves; c, capsule; d, part of peristome.
From Berkeley (1863, Plate 15). The approximate 1 cm scale applies to the whole plant (habit) illustrations only.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families (Bryophyta, Musci) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
