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BRYACEAE

(D. Holyoak)

Plants small to large and robust, growing as scattered plants or forming dense tufts. Stems erect, solitary or few-branched by innovations, or stems connected by stolons (Rhodobryum), usually radiculose, occasionally densely tomentose; in cross-section central strand present. Leaves spirally arranged, often small and distant below, equally spaced or distally rosulate, variously shaped, lanceolate, ovate, oblong, obovate, to broadly ovate or occasionally orbicular, apex broadly acute to acuminate, occasionally obtuse or rounded, base sometimes decurrent; margins plane to recurved or reflexed, entire to serrate distally, often sharply so, limbate or elimbate; costa single, evanescent to excurrent; laminal cells smooth (rarely slightly prorate), median cells typically short to long hexagonal or rhomboidal, sometimes linear and sinuose (Anomobryum), walls ± firm, porose or not; basal cells quadrate or short to long rectangular, lax- or firm-walled; alar region usually undifferentiated; marginal cells similar or long to linear if forming a border. Asexual propagules regularly present in some species, as rhizoidal tubers, as bulbils or cylindrical gemmae in leaf axils, or as protonemal tubers or gemmae. Autoicous, dioicous or synoicous. Perigonia bud-like. Perichaetia terminal (rarely appearing lateral when overtopped by subperichaetial innovations), bracts usually little differentiated, some larger than stem leaves but innermost often much smaller. Seta elongate, single or occasionally several together, smooth. Capsule exserted, mostly pendulous, but mainly erect or suberect in some genera, urn ovoid to obloid, or more often pyriform, usually with a distinct short or long neck; exothecial cells mostly elongate, firm and thick-walled, stomata at base of urn, superficial; annulus often large and revoluble, or absent. Operculum conic, conic-apiculate or shortly rostrate. Peristome mostly double or variously reduced or single; typically, exostome teeth 16, papillose and trabeculate; endostome basal membrane present, segments 16, keeled, hyaline or yellowish, cilia 2 or 3. Calyptra cucullate, naked and smooth. Spores spherical, usually lightly papillose.

Discussion. The genera Epipterygium, Mielichhoferia and Pohlia have recently been transferred to the Mniaceae, Orthodontium to the Orthodontiaceae, and Leptobryum to the Meesiaceae, mainly on the basis of DNA-sequence data (Cox & Hedderson 1999, Buck & Goffinet 2000). Following these transfers of genera to other families, the Bryaceae contains about 11 genera and almost 1000 species; in sub-Saharan Africa there are 6 genera and about 142 species.
    Recent studies of phylogenetic relationships within the Bryaceae based on chloroplast DNA evidence (Cox & Hedderson 2003, Pedersen et al. 2003) show that Bryum and Brachymenium are not monophyletic groups and that Anomobryum, Plagiobryum and Rhodobryum also belong to the same clade as these. Indeed, Anomobryum and Plagiobryum appear to be recent derivatives within the radiation of species of Bryum sensu lato, and hence unworthy of generic separation. At least for Anomobryum and Rhodobryum, these conclusions were anticipated to some extent by Ochi (1972, 1992) and some other taxonomists who made detailed morphological studies. There is thus a strong argument for placing all Bryaceae in Bryum, but the usual generic divisions are maintained here to prevent Bryum becoming an even larger and more unwieldy genus and because the merger of Brachymenium in Bryum would require new nomenclatural combinations. Comprehensive rearrangement of the generic taxonomy of Bryaceae seems inevitable in future but it is not attempted in this Guide because too few taxa have as yet been subject to detailed studies of DNA sequences and morphology. Rosulabryum (Spence 1996) is not treated as a separate genus from Bryum here because it is not monophyletic (Cox & Hedderson 2003: 38, Pedersen et al. 2003).

Study guide. The family is notoriously difficult and numerous taxonomic problems remain unresolved among its African species. While many of the species are distinct and readily recognisable given some experience, features of the peristome are critical in the identification of many taxa so that collections lacking mature capsules are frequently difficult or impossible to name. Ochi (1972) has provided an illustrated synoptical treatment that covers most of the Afrotropical Bryaceae.
    Species of Bryum often grow intermixed and they sometimes hybridise. Care is therefore needed to ensure that leaves and capsules are studied from the same plant. Stem leaves provide many of the essential features needed for identifying species. Sections of the costa should be made in the lowest one-third of the leaf. As noted above, characters of the intact peristome are often also needed, especially in Bryum and Brachymenium. 'Perfect peristomes' have the endostome fully developed with processes ± as long as exostome teeth and two or three long appendiculate cilia between each pair of processes. 'Reduced' endostomes have cilia short to rudimentary and the processes may also be shorter. Determining the sexuality of Bryum may be difficult because inflorescences are often partly decayed by the time capsules mature and the antheridia often decay without trace before the remnants of unused archegonia disappear.
    Species of Pohlia (Mniaceae) may show strong superficial similarity to Bryum spp., but these differ in (1) usually having relatively longer, narrower leaf cells, (2) often having the upper half of the leaf ± denticulate or toothed, (3) in always lacking a leaf border of narrow cells, and (4) the leaf section usually has several large median guide cells with stereids both above and below them (whereas Bryum lacks large guide cells and typically shows only a single dorsal band of stereids). One or another of those characters occurs in various species of Bryum, but rarely two or three together, except sometimes in Bryum alpinum which is probably the species of Bryum most prone to confusion with Pohlia spp., although it usually differs from them in having strong red pigmentation. Other characters helpful in separating Pohlia from Bryum are that the former genus has the costa ending in or below the leaf apex (costa often excurrent in Bryum), relatively longer perichaetial bracts in many species, and cilia rudimentary to long but not appendiculate as in some Bryum. Mielichhoferia (Mniaceae) differs from Bryaceae in the sporophytes quickly becoming lateral through elongation of a subperichaetial innovation and in the pyriform capsule having rudimentary exostome teeth much shorter than the endostome segments.

Literature. Buck, W.R. & Goffinet, B. 2000. Morphology and classification of mosses. Pp. 71-123, in Shaw, A.J. & Goffinet, B. Bryophyte Biology. Cambridge: Cambridge University Press. Cox, C.J. & Hedderson, T.A.J. 1999. Phylogenetic relationships among the ciliate arthrodontous mosses: evidence from chloroplast and nuclear DNA sequences. Plant Systematics and Evolution 215: 119-139. Cox, C.J. & Hedderson, T.A.J. 2003. Phylogenetic relationships within the moss family Bryaceae based on chloroplast DNA evidence. Journal of Bryology 25: 31-40. Ochi, H. 1972. A revision of the African Bryoideae, Musci (First part). Journal of the Faculty of Education, Tottori University, Natural Science 23: 1-126 [keys, illustrations]. Ochi, H. 1973. A revision of African Bryoideae (Second Part). Journal of the Faculty of Education, Tottori University, Natural Science 24: 23-50. Ochi, H. 1992. A revised infrageneric classification of the genus Bryum and related genera (Bryaceae, Musci). Bryobrothera 1: 231-244. Pedersen, N., Cox, C.J. & Hedenäs, L. 2003. Phylogeny of the moss family Bryaceae inferred from chloroplast DNA sequences and morphology. Systematic Botany 28: 471-482. Shaw, J. 1985. The correlation between taxonomy and peristome structure in the Bryaceae. Journal of the Hattori Botanical Laboratory 59: 79-100. Shaw, J. 1987. Systematic studies on the Bryaceae. Memoirs of the New York Botanical Garden 45: 682-690. Spence, J.R. 1996. Rosulabryum genus novum (Bryaceae). Bryologist 99: 221-225. Van Rooy, J. & Magill, R.E. 1987. Bryaceae, pp. 335-393, in Magill, R.E., Flora of Southern Africa. Bryophyta. Part 1 Mosses, Fascicle 2 Gigaspermaceae - Bartramiaceae. Dept. of Agriculture and Water Supply, Republic of South Africa [keys, illustrations].

Anomobryum Schimp.

Eight species in sub-Saharan Africa; worldwide there are about 25-30 species, many widely distributed.

Plants small and slender, gregarious or forming short tufts, lustrous, light green or yellowish, to golden-brown. Stems erect, simple or few branched, julaceous; in cross-section central strand present. Leaves appressed, ovate, obovate, ovate-oblong to short lanceolate, ca 1-2 mm long, concave, apex acute to obtuse or rounded, base slightly decurrent; margins plane, occasionally reflexed below, entire to finely serrulate; costa usually strong, subpercurrent to short excurrent; apical cells often short, rhomboidal; median cells linear to rhomboidal, often sinuose or vermicular, thin- or thick-walled; lower and basal cells enlarged, rectangular, thin-walled and lax; marginal cells not or ± weakly differentiated as a border of narrow elongate cells. Dioicous. Perichaetia terminal. Seta to 30 mm long, usually slender. Capsule inclined to pendulous, urn pyriform-cylindrical, neck short. Operculum conic, blunt to apiculate. Peristome double, rarely reduced, exostome teeth joined at base; endostome basal membrane high, segments keeled and perforate, cilia appendiculate. Spores spherical, finely papillose.

Habitat. On soil or rock ledges, often in wet or flushed sites, lowland to >3000 m.

Discussion. The julaceous stems and branches, and appressed leaves are similar to those of Bryum argenteum, but that common species differs in lacking chlorophyll in the upper parts of the leaves so the plants are whitish. The long, sinuose to vermicular upper lamina cells of several Anomobryum are distinctive in the Bryaceae, but other species have short (length:breadth <4:1) rhomboidal to hexagonal cells. Ochi (1980) placed Anomobryum as a subgenus in Bryum.

Literature. Ochi, H. 1972 (see family ref.). Shaw, J. & Fife, A.J. 1984. The evolutionary and taxonomic significance of peristome morphology in Anomobryum (Bryaceae, Musci). Journal of the Hattori Botanical Laboratory 57: 285-298. Van Rooy, J. & Magill, R.E. 1987 (see family ref.).

Brachymenium Schwägr.

33 species recorded for sub-Saharan Africa; a genus containing well over 100 species distributed in the tropics and extending into sub-temperate regions worldwide.

Plants small to large (2-35 mm), forming dense tufts, light or yellow-green to dark or brownish-green, often lustrous. Stems erect, simple to few branched, radiculose, occasionally tomentose; in cross-section central strand present. Leaves equidistant or rosulate, crispate to ± flexuose and erect to erect-spreading when dry, erect-spreading to spreading when wet, lanceolate, oblong-lanceolate, ovate or obovate-oblong, apex short to long acuminate, base slightly decurrent or not; margins limbate, plane above, often reflexed to recurved in lower 1/2, entire to more commonly serrulate or serrate; costa usually strong, short to long excurrent, rarely subpercurrent, in section with weak dorsal stereid band; awn smooth or toothed; median cells mostly thin-walled, broadly hexagonal or short to long rhomboidal-hexagonal, rhomboidal toward margin and apex; lower and basal cells short rectangular; apical cells occasionally differentiated, hyaline; marginal border cells linear and thick-walled, 1-4 rows. Propagula often present, as axillary bulbils in some species. Autoicous, synoicous or dioicous. Perichaetia terminal but often overgrown by subperichaetial innovations, bracts often larger than leaves. Seta 10-40 mm long, erect to weakly flexuose, slender to stout. Capsule suberect to commonly erect, less often inclined or horizontal, urn pyriform to cylindrical-pyriform or clavate, slightly asymmetrical, neck usually distinct, phaneropore stomata present on neck, mouth small to medium sized. Operculum short and hemispherical to long conic, rarely rostrate. Peristome double, exostome teeth with trabeculae well developed; endostome basal membrane low to high, segments rudimentary or well developed and narrowly perforated, cilia absent or rudimentary. Spores small or large, spherical, lightly papillose.

Habitat. Epiphytic on trees and shrubs, some species also on logs, humus, soil and rocks; lowland to at least 2800 m.

Discussion. Usually distinct from Bryum in the erect to suberect capsules and reduced endostome. Plants lacking capsules are often unidentifiable.

Literature. Ochi, H. 1972 (see family ref.). Van Rooy, J. & Magill, R.E. 1987 (see family ref.).

Bryum Hedw.

About 93 species are reported for sub-Saharan Africa, in this, the largest genus of the family. It is estimated that Bryum comprises nearly 800 species distributed worldwide but much taxonomic reassessment is needed.

Plants small to large and robust (2-100 mm), growing as scattered stems or more often forming loose to dense tufts, pale to dark green, reddish, brownish, yellowish, golden, blackish or ± bright red throughout. Stems erect, few to several branched by innovations, ± radiculose, occasionally densely tomentose; in cross-section central strand present. Leaves equidistant to more commonly crowded, sometimes rosulate, when dry plane to contorted or crispate, erect-appressed to erect, when wet erect-spreading or spreading, lanceolate, ovate, obovate, oblong, elliptical, or suborbicular, 0.5-7 mm long, apex acute to acuminate, less often rounded, base decurrent in some species; margins usually reflexed to recurved, less often plane, entire to more commonly serrulate or serrate at mid-leaf or above; costa evanescent or subpercurrent to ± long excurrent; upper and median laminal cells rhomboidal-hexagonal or hexagonal, rarely long-rectangular, porous or not; lower and basal cells quadrate to oblong or rectangular, thin to ± thick-walled, occasionally lax; marginal cells commonly forming a distinct border of incrassate linear cells. Asexual propagules regularly present in some species, as rhizoidal tubers, as bulbils or cylindrical gemmae in leaf axils, or as protonemal tubers or gemmae. Dioicous, autoicous or synoicous. Perigonia usually bud-like. Perichaetia terminal, bracts differentiated or not. Seta 8-50 mm long. Capsule inclined or pendulous (less often suberect or horizontal, but usually only in poorly grown plants or those on steep substrata), urn short to long oblong, cylindrical or pyriform, 1-5 mm long; neck short or long; phaneropore stomata at urn base; annulus compound, revoluble. Operculum convex-conic or conic-apiculate to shortly rostrate. Peristome double, exostome teeth joined at base, mostly papillose, distally smooth, trabeculate; endostome lightly papillose, basal membrane ± high, segments keeled and perforate, cilia appendiculate or nodose, sometimes rudimentary or absent. Spores spherical, ± weakly papillose.

Habitat. Commonly on soil, humus and rocks, less often epiphytic (but frequently so in the widespread B. capillare) or on logs; from lowlands to 4920 m. Some species tolerate seasonally dry soils in savannas, others are confined to permanently wet habitats in mires or beside springs or streams.

Discussion. A large and highly variable genus, both gametophytically and sporophytically. Some species can be identified from non-fertile specimens but others require study of undamaged peristomes and mature spores. Bryum is one of the most difficult genera of mosses, partly because of morphological plasticity of some species and partly because of hybridisation. A modern worldwide revision might result in half of the number of species currently recognised.

Literature. Mohamed, M.R.1979. A taxonomic study of Bryum billardieri Schwaegr. and related species. Journal of Bryology 10: 401-465 [keys, illustrations]. Ochi, H. 1972 (see family ref.). Van Rooy, J. & Magill, R.E. 1987 (see family ref.).

Perssonia Bizot

One species, P. sanguinea Bizot, known only from Cape Verde Islands.

Plants small (2-5 mm) in lax red tufts. Stems erect, with slender branches, not tomentose. Leaves ± equidistant, erect-spreading and flexuose when dry, spreading when moist, ovate-lanceolate, slightly concave, entire, margins plane, costa excurrent; few basal cells sub-quadrate, cells above uniformly hexagonal, narrower at margins but leaves not bordered. Apparently dioicous. Seta erect, 20 mm long. Capsule horizontal to cernuous, 3 mm long, with long neck; exothecial cells in middle of urn rectangular, ± sinuose; phaneropore stomata at urn base; annulus compound, persistent or perhaps caducous. Operculum conical. Peristome double, exostome teeth narrow, densely papillose on both surfaces, trabeculate; endostome reduced, basal membrane short (1/8 height of exostome teeth) hyaline, slightly papillose, and apparently adherent to exostome, processes divided into two branches, one branch red-brown, as long as exostome teeth, uniseriate, nodulose at articulations, the other a short rudiment; cilia lacking. Immature spores smooth.

Habitat. Collected at 450-1200 m; habitat and substratum not reported.

Discussion. This monotypic genus is recognised as distinct from Bryum only because of the peculiar asymmetrical reduction of each of its endostome segments. The Neotropical Acidodontium also has forked segments but they have two branches of ± equal length. Nevertheless, further study seems likely to show that Perssonia is a member of the same clade as Bryum and Brachymenium.

Literature. Bizot, M. 1969. Mousses des Iles du Cap Vert. Svensk Botanisk Tidskrift 63: 441-454 [illustrations].

Plagiobryum Lindb.

Three species recorded for sub-Saharan Africa; worldwide there are six species, four in the Northern and two in Southern Hemisphere.

Plants small (4-10 mm), forming dense soft tufts or mats, light green to hyaline with reddish tint, sparsely radiculose below. Stems erect, few or several branched by innovations, branches julaceous. Leaves imbricate, erect when wet and dry, ± broadly ovate, concave, 0.6-1.0 mm long; apex acute, hyaline; margins plane or slightly reflexed, entire to weakly toothed distally; costa evanescent or subpercurrent to excurrent, somewhat flexuose; laminal cells thin-walled, lax, hyaline, upper and median cells rhomboidal to rhomboid-hexagonal (2-4:1); upper marginal cells narrower, not forming distinct border; basal cells shorter. Dioicous. Perigonia terminal or lateral through innovation. Perichaetia terminal, frequently overgrown by subperichaetial innovations; perichaetial bracts longer than leaves, ovate-lanceolate. Seta rather short, 3-10 mm long, stout, curved distally, smooth. Capsule horizontal to pendulous, clavate or gibbous, to 5 mm long, asymmetric, mouth oblique, narrowed, neck differentiated, 1-2 mm long; phaneropore stomata numerous on neck; annulus revoluble. Operculum conic. Peristome double, exostome teeth rather short, shorter than endostome, weakly papillose or cross-striate below, distally smooth; endostome adhering somewhat to exostome, basal membrane rather high, segments irregular, narrowly keeled, perforate above, cilia rudimentary. Spores rather large, ellipsoidal, forming tetrads until maturity, coarsely papillose.

Habitat. At high altitudes, on soil on cliff faces or in rock crevices.

Discussion. The small whitish or silvery plants are rather similar to those of Bryum argentum, from which non-fertile material can be distinguished by the lax upper laminal cells and pinkish lower parts of the plants. Plagiobryum with capsules are easily separated from B. argenteum by the distally curved, short seta, clavate capsule that is asymmetrical with an obliquely oriented mouth, weakly ornamented short exostome teeth (less than 250 µm), and endostome exceeding the exostome.

Literature. Ochi, H. 1972. (see family ref.). Shaw, A.J. 1982. Plagiobryum zieri (Hedw.) Lindb. disjunct in Guatemala, with phytogeographic notes. Bryologist 85: 243-250 [illustrations]. Van Rooy, J. & Magill, R.E. 1987. (see family ref.).

Rhodobryum (Schimp.) Limpr.

Four species in sub-Saharan Africa; a genus containing some 40 species widely distributed in cool temperate regions, in the tropics largely confined to the highlands.

Plants large to more often robust, to 70 mm tall, forming loose to dense tufts, dark green to reddish-brown. Stems erect, often connected by underground stolons, few to several branched by innovations, radiculose, often densely tomentose. Leaves rosulate, with large leaves distally or interruptedly in crowded rosettes, or ± equally spaced small leaves, mostly erect to erect-spreading and ± crispate when dry, erect-spreading to wide-spreading when wet, oblong-obovate to oblong, mostly 7-12 mm long, to 5 mm wide, apex obtuse to acute and often apiculate, rarely acuminate, base usually shortly decurrent; margins distally plane, below plane or narrowly reflexed or recurved, occasionally undulate, limbate, serrate, often sharply so, or serrulate; costa strong below and usually weak distally, short excurrent, in cross-section with ventral cells in 3 or more rows and dorsal stereid or substereid band small or absent; upper and median cells rhomboidal to hexagonal, thin- to ± thick-walled, often weakly to strongly porose; basal cells long-rectangular; marginal border cells linear to linear-rhomboidal, 2-6 rows, ± thick-walled. Dioicous. Perigonia and perichaetia terminal. Seta 1 or 2, 20-80 mm long, rather stout. Capsule horizontal to pendulous, urn long cylindrical or cylindrical-pyriform, frequently curved, 4-6 mm long, neck short, frequently wrinkled when dry; stomata open. Operculum conic-apiculate. Peristome double, exostome teeth lightly papillose, trabeculate; endostome basal membrane high, segments perforate and keeled, cilia well developed, appendiculate. Spores lightly papillose.

Habitat. On soil or humus; in the tropics mostly in premontane to montane forests (ranging from at least 1200-3500 m), but in the lowlands in southernmost Africa.

Discussion. The genus is recognized by the large plants, with rosulate leaves often 7->10 mm long, and usually with weakly to strongly bordered margins. Distinction from the largest species of Bryum also relies on the presence of stolons and the cross-section of the costa (see key). Ochi (1972), among other authors, treats Rhodobryum as a subgenus of Bryum.

Literature. Ochi, H. 1972. (see family ref.). Van Rooy, J. & Magill, R.E. 1987. (see family ref.).

accepted 17.04.2003