The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



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.

British representation. 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. Discelium nudum. • Catoscopiaceae and Disceliaceae: Berkeley.

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 moss families of the British Isles. Version: 21st June 2009.’.