The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Gametophyte. Plants “normal”, with leaves containing chlorophyll. Acrocarpous; cushion-forming, or forming tufts. Mature plants 0.5–2 mm high (Campylostelium), or 5–40 mm high. The leaves neither sphagnoid nor leucobryoid. The leaves lanceolate to linear; spiral; crisped when dry; single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip. Leaf blades not lamellate. Leaf blade apices pointed; acuminate; not hyaline. Leaf blade margins flat, or revolute or recurved; irregularly denticulate to dentate, or entire. Leaf blades not conspicuously bordered. The basal leaf cells longitudinally much elongated; rectangular (to narrowly rectangular), or rounded, or rhomboidal; smooth. The walls of basal leaf cells thin to thick; straight. The angular cells not well differentiated. The mid-leaf cells more or less isodiametric, or more or less isodiametric to somewhat longitudinally elongated; small, quadrate, or rectangular, or rounded; smooth. The walls of the mid-leaf cells thick; straight.

Sporophyte. Capsules emergent or exserted; erect; straight; ellipsoid to ovoid; without an externally conspicuous apophysis; smooth. Calyptra campanulate, symmetrical; plicate (in Ptychomitrium), or not plicate (?); with two or more splits (in Campylostelium,), or tearing irregularly (laciniate, in Glyphomitriumium). Capsules with a peristome. The peristome single. The peristome teeth 16; not grouped, or in pairs (Glyphomitrium); deeply cleft (bifid, in Ptychomitrium and Campylostelium), or not deeply cleft; not perforated, or perforated; thin, membranous, and transversely barred; without longitudinal dividing lines. The operculum rostrate, or subulate. Setae short to long; straight, or curved, or flexuose.

Ecology. Occurring in basic habitats, or neutral pH conditions, or acid conditions. Ptychomitrium on exposed acidic rocks and wall tops; Glyphomitrium on acidic or basic rocks in coastal areas, and basic rocks inland; Campylostelium on shaded sandstone and slatey rocks.

Cytology. Haploid chromosome number, n = 13 (in Ptychomitrium polyphyllum).

British representation. 3 species. Campylostelium (Bent-moss), Glyphomitrium (Black-tufted moss), Ptychomitrium (Long-shanked Pincushion). Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, central southern England, southwest England, Isle of Wight, and Ireland.

Classification. Class Bryopsida; Subclass Dicranideae; Order Grimmiales.

Illustrations. • Campylostelium, Coscinodon, Glyphomitrium, Ptychomitrium: Dixon. • Ptychomitrium and Glyphomitrium, with Grimmiaceae and Hedwigiaceae: 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.’.