The moss families (Bryophyta, Musci) of Britain and Ireland

L. Watson and M.J. Dallwitz

Pottiaceae

Tufa-mosses, Screw-mosses, Crisp-mosses, Stubble-mosses, Pottias, etc.

Dixon’s Tortulaceae; excluding Cinclidotaceae (Cinclidotus)

Gametophyte. Always or nearly always acrocarpous (sometimes hygroscopic); cushion-forming, or forming tufts, or mat or turf forming, or forming patches, or the plants scattered. Rosette plants (often, more or less), or non-rosette plants. Mature plants 1–80(–120) mm high (but with numerous species reaching no more than about 2–3 mm, including Stegonia latifolia, which takes the form of tiny, stemless, bud-like plants). Plants exhibiting comal tufts of leaves (rarely), or without comal tufts. Shoots not complanate. Stems not tomentose; with a differentiated central strand, or without a differentiated central strand. The leaves neither sphagnoid nor leucobryoid. The leaves lingulate to obovate, or ovate, or lanceolate to linear (but generally ovate or spathulate, rarely narrow); spiral; not secund (almost invariably, though sometimes secund in Oxystegus tenuirostris); crisped when dry (commonly, e.g. in Tortula, Didymodon, Tortella, etc.), or not crisped when dry (e.g., Pottia). Leaf bases sheathing, or not sheathing. The leaves single-nerved. The leaf nerves extending to the leaf tip; excurrent (commonly, often conspicuously so), or not excurrent. Leaf blades adaxially longitudinally lamellate (with 4 lamellae, in species of Pottia and in Tortula Section Pterygoneurum), or not lamellate. Leaf blade apices obtuse, or pointed; apiculate, or not apiculate; apically rounded, or apically acute, or acuminate; conspicuously hyaline (commonly, via the excurrent nerve), or not hyaline. Leaf blade margins flat, or involute or incurved, or revolute or recurved; unistratose (usually), or bi-stratose (e.g., in the mid-section, in Trichostomopsis). Leaf blades bordered (notably in Tortula), or not conspicuously bordered. The basal leaf cells more or less isodiametric to somewhat longitudinally elongated, or longitudinally much elongated; rectangular, or rounded; papillose, or smooth. The walls of basal leaf cells usually thin (generally lax and hyaline), or thick (notably in Barbula); straight. The angular cells clearly differentiated, or not well differentiated. The mid-leaf cells more or less isodiametric, or more or less isodiametric to somewhat longitudinally elongated; quadrate, or rectangular, or hexagonal, or rounded; papillose (often), or smooth. The walls of the mid-leaf cells thin to thick; straight.

Plants monoecious, or dioecious (commonly or exclusively in some genera); when monoecious, autoecious (commonly), or paroecious, or synoecious (rarely). Plants gemmiferous (e.g., in some Tortula and Leptodontium), or not gemmiferous; the gemmae when present, borne on the leaf nerves and laminae.

Sporophyte. Capsules immersed (e.g., some Weissia and Phascum species, Acaulon), or emergent to exserted (sometimes slightly exserted in Phascum), or exserted; erect (usually), or erect to pendulous; symmetrical, or symmetrical to asymmetrical; straight (usually, more or less), or curved; globose (e.g., Pottia recta, Phascum spp.), or sub-cylindric, or ellipsoid (or obloid), or ovoid; without an externally conspicuous apophysis; smooth; with an annulus, or without an annulus. Calyptra symmetrical; splitting down one side, or with two or more splits. Capsules cleistocarpus (e.g., Weissia spp., Acaulon), or dehiscing via a lid; with a peristome, or without a peristome (in some Pottia species, Acaulon). The peristome single (often basally joined into a spirally twisted tube). The peristome teeth when present, 16, or 32; conspicuously spirally twisted (commonly), or not spirally twisted; joined basally to form a membranous ring, or not basally joined; deeply cleft, or not deeply cleft; not perforated, or perforated; thin, membranous, and transversely barred; when present and not cleft to the base into 32 teeth, interiorly exhibiting a fine longitudinal dividing line between the transverse bars. The operculum conical (e.g., Desmatodon), or rostellate to rostrate. Setae short to long; straight (usually), or straight to curved, or curved, or flexuose.

Ecology. Aquatic (Pleurochaete), or in wet places, or mesophytic, or xerophytic. Not saxicolous. In diverse habitats, but mostly terrestrial rather than rupestral.

Cytology. Haploid chromosome number, n = 11, 12, 13, 14, 15, 16, 20, 21, 24, 25, 26, 27, 28, 36, 40, 42, 48, 50, 52, 55, and 56 (etc.?, sometimes with supernumeraries, and numerous species not recorded).

Representation in Britain and Ireland. About 110 species. Acaulon (Pygmy-mosses), Aloina (Aloe-mosses), Anoectangium (Summer-moss), Barbula (Bird’s-claw Beard-mosses), Bryoerythrophyllum (Beard-mosses), Dialytrichia (Pointed Lattice-moss), Didymodon (Beard-mosses), Eucladium (Whorled Tufa-moss), Gymnostomum (Tufa-mosses), Gyroweisia (Beardless- and Stubble-mosses), Hennediella, Hymenostylium (Tufa-mosses), Leptobarbula (Beric Beard-moss), Leptodontium (Beard- and Thatch-mosses), Leptophascum (Vectis-moss), Microbryum, Molendoa (Warburg’s Moss), Paraleptodontium (Drooping-leaved Beard-moss), Phascum (Earth-mosses), Pleurochaete (Side-fruited Crisp-moss), Pottia (Pottias), Pottiopsis (Pottias), Protobryum (Pottia), Pseudocrossidium (Beard-mosses), Pterygoneurum (Chalk-moss, Pottia), Scopelophila (Tongue-leaf Copper-moss), Stegonia (Hood-leaved Screw-moss), Syntrichia (Screw-mosses), Tortella Crisp-mosses), Tortula (Screw-mosses), Trichostomopsis, Trichostomum (Crisp-mosses), Weissia (Beardless- and Stubble-mosses). 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 Pottiales.

Comments. Thus circumscribed, an alarmingly diverse family which may be impossible to define satisfactorily.

Illustrations. • Acaulon, Phascum, Microbryum etc., with Hedwigiaceae: Dixon. POTTIACEAE: C, Acaulon muticum (Brid.) C. Müll.; D, Acaulon triquetrum (Spruce) C. Müll.; E, Phascum cuspidatum Hedw.; F, Phascum floerkeanum Web. & Mohr.; G, Microbryum curvicolle (Hedw.) Zander; H, Microbryum rectum (With.) Zander; I, Pottia bryoides (Dicks. ) Mitt.; J, Hennediella heimii (Hedw.) Zander.; K, Tortula truncata (Hedw.) Mitt. HEDWIGIACEAE: A, Hedwigia ciliata (Hedw.) P. Beauv.; B, Hedwigia integrifolia P. Beauv.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Tortula, Pottia, Pottiopsis, Pterygoneurum and Stegonia. POTTIACEAE: A, Tortula modica Zander; B, Tortula viridifolia (Mitt.) Blockeel & Sm.; C, Tortula wilsonii (Hook.) Zander; D, Tortula viridifolia (Mitt.) Blockeel & Sm.; E, Tortula wilsonii (Hook.) Zander; F, Pottia starkeana (Hedw.) C. Müll. ssp. minutula; G, Pottia starkeana ssp. starkeana; H, Pottia davalliana (Sm.) Jensen; I, Pottiopsis caespitosa (Brid.)Blockeel & Sm.; J, Tortula lanceola Zander; K, Stegonia latifolia (Schwaegr.) Vent. ex Broth.; L, Pterygoneurum ovatum (Hedw.) Dix.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Aloina, Pterygoneurum and Tortula: Dixon. POTTIACEAE: A, Pterygoneurum lamellatum (Lindb.) Jur.; B, Aloina brevirostris (Hook. & Grev.) Kindb.; C, Aloina aloides (Schultz) Kindb.; D, Aloina rigida (Hedw. ) Limpr.; E, Aloina ambigua (B.& S.) Limpr.; F, Tortula cernua (Hüb.) Lindb.; G, Tortula leucostoma (R.W. Br.) Hook. & Grev.; H, Tortula atrovirens (Sm.) Lindb.; I, Tortula cuneifolia (With.) Turn,; J, Tortula vahliana (Schultz) Mont.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Bryoerythrophyllum, Didymodon and Syntrichia: Dixon. POTTIACEAE: A, Syntrichia ruralis (Hedw.) Weber & Mohr; B, Syntrichia ruralis ssp. ruraliformis (Besch.) Dix.; C, Syntrichia papillosa (Wilson) Jur.; D, Syntrichia norvegica F. Weber; E, Syntrichia princeps (De Not) Mitt.; F, Didymodon luridus Hornsch. ex Spreng.; G, Didymodon cordatus Jur.; H, Bryoerythrophyllum recurvirostrum (Hedw.) Chen; I, Didymodon tophaceus (Brid.) Lisa; J, Didymodon fallax (Hedw.) Zander.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Didymodon and Pseudocrossidium: Dixon. POTTIACEAE: A, Didymodon ferrugineus (Schimp. and Besch.) Hill; B, Didymodon spadiceus (Mitt.) Limpr.; C, Didymodon rigidulus Hedw.; D, Didymodon glaucus Ryan; E, Didymodon nicholsonii Culm.; F, Didymodon insulanus (De Not) Hill; G, Didymodon vinealis (Brid.) Zander; H, Didymodon sinuosus (Mitt.) Delogne; I, Didymodon acutus (Brid.)K. Saito; J, Barbula icmadophila C. Müll. (current generic assignment uncrtain); K, Pseudocrossidium hornschuchiana (Schultz) Zander; L, Pseudocrossidium revolutum (Brid.) Zander.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Barbula (2 species), Leptodontium (2 species) and Weissia (9 species): Dixon. POTTIACEAE: A, Barbula convoluta Hedw.; B, Barbula unguiculata Hedw.; C, Leptodontium gemmascens (Dicks.) Hampe; D, Leptodontium flexifolium (Withe.) Hampe; E, Paraleptodontium recurvifolium (Tayl.) Long; F, Weissia longifolia Mitt. var longifolia; G, Weissia sterilis Nicholson; H, Weissia multicapsularis (Sm.) Mitt.; I, Weissia X mittenii (Br. Eur.) Mitt.; J, Weissia rostellata (Brid.) Lindb.; K, Weissia squarrosa (Nees & Hornsch.) C. Müll.; L, Weissia brachycarpa (Nees & Hornsch) Jur; M, Weissia condensa (Voit) Lindb.; N, Weissia controversa Hedw. var. crispata (Nees & Hornsch.) Nyholm.

From Dixon (1924), the unscaled screen display approximately doubling the magnifications given with his individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. • Dialytrichia, with Cinclidotus: Dixon. POTTIACEAE: F, Dialytrichia mucronata (Brid.) Broth.

From Dixon and Jameson (1924), the unscaled screen display approximately doubling the magnifications given with their individual figures. 1, leaf or stem leaf where these differ; 2, branch-leaf; 3, perichaetial leaf; 4, perigonial leaf; 5, capsule; 6, peristome; 7, calyptra; 8, spores; 9, inflorescence; 10, gemmae; 11, paraphyllia; 12, stoma of capsule; *, plant, or part of one. CINCLIDOTACEAE: G, Cinclidotus fontinaloides (Hedw.) P. Beauv. Qualifications: a, apex; b, base; c, cells at one third from the apex; cv, ventral aspect of cells; cd, dorsal aspect of cells; bc, basal cells; x, section. C. fontinaloides. D. mucronata. • Syntrichia, Pottia and Tortula, with Cinclidotus: Berkeley. POTTIACEAE: 1, Protobryum bryoides (Dicks.) Guerra and Cano., habit; a, plant enlarged; c, leaf; d, capsule. 3, Tortula muralis Hedw.; a, habit; b, leaf; c, capsule with calyptra; d, capsule with lid intact. 4, Syntrichia ruralis (Hedw.) Weber & Mohr var. ruralis; a, habit; b, leaf; c, capsule; d, peristome; e, detail of part of peristome. 5, Tortula atrovirens (Sm.) Lindberg; a, habit; b, leaf; c, capsule; d, capsule after fall of lid; e, part of peristome. CINCLIDOTACEAE: 2, Cinclidotus fontinaloides (Hedw.) P. Beauv.; a, habit; b, leaf; c, calyptra; d, capsule; e, part of the peristome, and the tip of the columella with some teeth wound round it.

From Berkeley (1863, Plates 14, 22 and 24). The approximate 1 cm scale applies to the whole plant (habit) illustrations only. • Tortula spp. and Hennediella: Berkeley. POTTIACEAE: 1, cf. Tortula lanceolata Zander; a, habit; b, leaf; c, capsule; d, capsule without lid; e, part of peristome. 2, Tortula viridifolia (Mitt.) B. & S.; a, habit; b, leaf; c, calyptra; d, capsule; e, follicle of “Pottia cavifolia”. 3, Hennediella heimii (Hedw.) Zander; a, habit; b, leaf; c, capsule. 4, Tortula atrovirens (Sm.) Lindb.; a, habit; b, leaf; c, capsule; d, capsule without lid; e, part of peristome.

From Berkeley (1863, Plates 22 and 23). The approximate 1 cm scale applies to the whole plant (habit) illustrations only. • Weissia controversa and W. squarrosa: Berkeley. POTTIACEAE: 6, Weissia controversa Hedw.; a, habit; b, leaf; c, capsule; d, part of peristome. 7, Weissia squarrosa (N. & H.) C. Müll.; a, habit; b, plant more enlarged; c, leaf; d, capsule; e, mouth of capsule.

From Berkeley (1863, Plate 24). The approximate 1 cm scale applies to the whole plant (habit) illustrations only. • Anoectangium aestivum (as compactum: Berkeley). Anoectangium compactum, = A. aestivum (Hedw.) Mitt. a and b, sporangia entire and dehisced; c, leaf; d, leaf cells. Berkeley (1863), Plate 14. • Tortula subulata: Curtis (1825).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, 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. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2005 onwards. The moss families (Bryophyta, Musci) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.

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