The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Formerly included in Buxbaumiaceae.

Gametophyte. Acrocarpous; forming patches, or the plants scattered. Minute, almost stemless plants. Mature plants about 0.5–5 mm high. Leaves present. The leaves lanceolate, or lingulate; crisped when dry. Leaf bases slightly sheathing to not sheathing. The leaves single-nerved. The leaf nerves extending beyond the middle of the leaf, but not to the tip (though excurrent in the perichaetial leaves). Leaf blade apices obtuse to pointed; apically rounded to apically acute. Leaf blade margins unistratose (the body of the lamina unistratose basally, but 2(-3) stratose above). The basal leaf cells more or less isodiametric to somewhat longitudinally elongated; rectangular, or hexagonal, or rounded; 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; quadrate to rhomboidal; papillose. The walls of the mid-leaf cells thick; straight.

Plants dioecious.

Sporophyte. Capsules immersed to emergent (sub-sessile); inclined; asymmetrical; slightly curved, or straight; obliquely ovoid, or gibbous (somewhat); with an externally conspicuous apophysis, or without an externally conspicuous apophysis. Calyptra very small; symmetrical. Capsules with a peristome. The peristome single (representing the inner peristome, cf. haplolepideous mosses in general, but as in Buxbaumia taking the form of a pale, plicate membrane). The inner peristome with only 16 longitudinal plicae, contrasting with the 34-plicate membrane of Buxbaumia. The operculum narrowly conical. Setae short or long; straight.

Cytology. Haploid chromosome number, n = 9.

British representation. 1 species (D. foliosum being common in montane areas, rare elsewhere). Diphyscium (Nut-moss). Northern Scotland, southern Scotland, northern England, English Midlands, Wales, central southern England, southwest England, and Isle of Wight.

Classification. Class Bryopsida; Subclass Diphysciideae; Order Diphysciales.

Illustrations. • Diphyscium foliosum, with Buxbaumia: Dixon. Buxbaumia aphylla. Buxbaumia viridis. Diphyscium foliosum. • Diphyscium foliosum, with Buxbaumia aphylla: 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.’.