The Moss Families of the British Isles


L. Watson and M. J. Dallwitz



Gametophyte. Pleurocarpous; mat or turf forming. Primary stems procumbent (the branches erect or procumbent). Mature plants with stems to 50 cm long. Paraphyllia absent?. Stems not tomentose (but the older parts with sparse, thin rhizoids). The leaves of main stems and branches similar in form; ovate (concave); spiral; double-nerved to single-nerved. The leaf nerves not extending beyond the middle of the leaf (when single, sometimes to about halfway). Leaf blade apices obtuse, or pointed; apiculate, or not apiculate; truncate to apically rounded. Leaf blade margins proximally revolute or recurved, or flat; distally denticulate, or entire. The basal leaf cells somewhat longitudinally elongated to longitudinally much elongated; rhomboidal to linear, or vermicular; papillose. The walls of basal leaf cells straight. The angular cells clearly differentiated (these quadrate). The mid-leaf cells somewhat longitudinally elongated to longitudinally much elongated (2 to 6 times as long as wide); rhomboidal to linear, or vermicular; papillose (with one abaxial papilla per cell). The walls of the mid-leaf cells straight.

Plants dioecious.

Sporophyte. Capsules exserted; erect; symmetrical; straight; sub-cylindric; without an externally conspicuous apophysis; with an annulus (this falling with the operculum). Calyptra symmetrical; splitting down one side. Capsules with a peristome (this small, the outer teeth and the processes short). The peristome double. The peristome teeth not grouped; not deeply cleft; thin, membranous, and transversely barred; exteriorly with a fine longitudinal dividing line between the transverse bars. The inner peristome shorter than the outer; without a basal membranous ring; with elongated “processes”. The processes of the inner peristome 16 (these short and irregular). The inner peristome without cilia. The operculum rostrate. Setae long; straight.

Ecology. Occurring in basic habitats. Montane, on basic rocks and tree branches and roots.

British representation. 1 species. Pterigynandrum. Northern Scotland, southern Scotland, northern England, Wales, and Ireland.

Classification. Class Bryopsida; Subclass Bryideae; Order Hypnales.

Comments. Pterigynandrum was referred to Hypnaceae-Entodonteae by Watson (1978), and was an obvious misfit in Smith's (1978) Leskeaceae. It is certainly preferable to follow O'Shea and Wiggington’s (2004) check-list of African mosses in treating it as a monogeneric family. Both Heterocladium and Myurella are presented under Pterigynandraceae in some recent classifications, but pending acquisition of adequate comparative descriptive data, they are retained here in Thuidiaceae and Theliaceae, respectively.

Illustrations. • Pterigynandrum filiforme. Pterigynandrum filiforme. • Heterocladium: Dixon.

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.’.