The Moss Families of the British Isles


L. Watson and M. J. Dallwitz


Excluding Pterigynandraceae, Theliaceae, Thuidiaceae and Leptodon (Neckeraceae).

Gametophyte. Pleurocarpous; not dendroid; mostly forming patches, or forming wefts. Primary stems procumbent (the branches erect or procumbent). Shoots not complanate. Paraphyllia present (sparse or numerous), or absent. Pseudoparaphyllia absent. Stems not tomentose. The leaves of main stems and branches similar in form; ovate to lanceolate (concave); spiral; (sub-) secund (or the tips turned to one side, when moist), or not secund; double-nerved, or single-nerved. The leaf nerves not extending beyond the middle of the leaf, or extending beyond the middle of the leaf, but not to the tip. Leaf blade apices obtuse, or pointed; apically rounded, or apically acute, or acuminate. Leaf blade margins flat, or revolute or recurved; entire, or denticulate. Leaf blades not conspicuously bordered. The basal leaf cells more or less isodiametric to longitudinally much elongated (short save in some Lescuraea species); quadrate, or rectangular, or rounded, or rhomboidal to linear (in some Lescuraea species); papillose, or smooth. The walls of basal leaf cells thin, or thick; straight. The angular cells clearly differentiated, or not well differentiated. The mid-leaf cells more or less isodiametric to somewhat longitudinally elongated, or longitudinally much elongated (in Lescuraea and Ptychodium); quadrate, or rectangular, or hexagonal, or rounded, or rhomboidal to vermicular; papillose, or smooth. The walls of the mid-leaf cells thin, or thick; straight.

Plants monoecious, or dioecious; when monoecious, autoecious.

Sporophyte. Capsules exserted; erect to inclined; symmetrical, or symmetrical to asymmetrical; straight, or curved; sub-cylindric to ovoid; smooth; with an annulus, or without an annulus. Calyptra symmetrical; splitting down one side. Capsules with a peristome. The peristome double. The peristome teeth joined basally to form a membranous ring (in Lescuraea), or not basally joined (?); not grouped; not deeply cleft; thin, membranous, and transversely barred; exteriorly with a fine longitudinal dividing line between the transverse bars. The inner peristome reduced to rudimentary; about equalling the outer to exceeding the outer; with a basal membranous ring (this short); with elongated “processes”; without cilia (or rudimentary). The operculum conical to rostrate. Setae long; straight.

Ecology. In wet places to xerophytic; occurring in basic habitats, or neutral pH conditions. Mostly on rocks at high altitudes, but Leskea polycarpa is common at low altitudes and is often found silt-encrusted on tree roots, trunks and branches, and by pools, streams and rivers (sometimes in flood zones).

Cytology. Haploid chromosome number, n = 10 and 11 (and 11 + 2, with only Leskea polycarpa sampled).

British representation. 7 species. Leskea (Many-fruited Leskea), Lescuraea (Rock Feather-moss), Pseudoleskeella (Chained Leskea), Ptychodium (Plaited Leskea). Northern Scotland, southern Scotland, northern England, English Midlands, East Anglia, Wales, southeast England, central southern England, southwest England, and Isle of Wight (mostly northern, with the exception of Leskea polycarpa).

Classification. Class Bryopsida; Subclass Bryideae; Order Hypnales.

Illustrations. • Lescuraea, Leskea and Pseudoleskeella: Dixon. Leskea polycarpa Hedw. Pseudoleskeella nervosa (Brid.) Nyholm. Pseudoleskea incurvata (Hedw.) Loeske. Pseudoleskea patens (Linb.) Kindb. Pseudoleskeella catenulata (Brid.) Kindb. Lescuraea saxicola (Schimp.) Milde. • Ptychodium: Dixon. Ptychodium plicatum. • Ptychodium, with Brachytheciaceae, Orthothecium and Tomentypnum: 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.’.