Rosulabryum

Plants small to large, in open to dense low turfs or gregarious (tall turfs in R. andersonii), green to red-green. Stems 0.3–6 cm, usually strongly rosulate, sometimes in 2 or more interrupted rosettes, rarely evenly foliate or subjulaceous, subfloral innovations common; rhizoids often many, micronemata and macronemata present. Leaves variously contorted to spirally twisted around stem when dry or rarely nearly imbricate, erect to erect-spreading when moist, ovate, obovate, or spathulate, flat or weakly concave, 0.4–4.5 mm; base sometimes decurrent; margins recurved proximally or sometimes plane, plane distally, nearly entire to distinctly serrate near apex, 1-stratose, limbidium present or absent; apex broadly rounded to acute; costa sometimes not reaching apex, usually short- to long-excurrent, awn pigmented or hyaline, stereid band well developed, guide cells present, in 1 (or 2) layers; alar cells not differentiated; laminal areolation heterogeneous; proximal laminal cells rectangular, longer than more distal cells, 2–4:1; medial and distal cells rhomboidal, 3–5:1, walls thin to thick, sometimes porose. Specialized asexual reproduction common, by rhizoidal tubers or filiform leaf axil gemmae. Sexual condition dioicous, rarely synoicous, polyoicous, or autoicous; perigonia and perichaetia appearing terminal or lateral; perigonial leaves often enlarged and distinctly rosulate; perichaetial leaves same size as vegetative leaves, not forming rosette, inner leaves differentiated, more acuminate. Seta single, rarely double or triple, straight. Capsule nutant to inclined, clavate to cylindric or rarely pyriform, 2–6 mm; hypophysis little differentiated; operculum short-conic to umbonate; peristome double; exostome yellow, teeth lanceolate to narrowly lanceolate; endostome well developed, not adherent to exostome, basal membrane high, 1/2–2/3 exostome length, segments same height as exostome, widely perforated, cilia 2 or 3, appendiculate. Spores shed singly, 8–20 µm, smooth to finely papillose, dark yellow.

Distribution

Nearly worldwide, concentrated in the Southern Hemisphere, especially Africa, and in subtropical to tropical mountains.

Discussion

Species ca. 80 (13 in the flora).

Rosulabryum is a large, distinctive genus mainly found in tropical mountainous areas and in the Southern Hemisphere in areas of seasonal temperate climates, occurring typically on soil, less commonly on rock or wood, rarely epiphytic. The center of diversity appears to be sub-Saharan Africa.

Most Northern Hemisphere bryologists are not familiar with the great morphological diversity of the species of Rosulabryum sect. Rosulabryum, traditionally placed in Bryum sect. Rosulata (Müller Hal.) J. J. Amann, as very few taxa extend beyond 20° N latitude. The most widespread representatives of Rosulabryum in the Northern Hemisphere are the small somewhat atypical species of Bryum sect. Trichophora J. J. Amann centered on R. capillare. Recent molecular work suggests that this section of Rosulabryum may be closer to Ptychostomum, and thus convergent on the robust Rosulata clade of the genus. However, very few species have been sampled for molecular work, and it seems unlikely that the complex of characters defining Rosulabryum could have evolved twice in unrelated clades. Plants of Rosulabryum have concolorous leaf apices and symmetric capsules. The rhizoidal tubers, when present, are spheric; the endostome is papillose.

Selected References

None.

Lower Taxa

Rosulabryum andersonii, Rosulabryum andicola, Rosulabryum bornholmense, Rosulabryum canariense, Rosulabryum capillare, Rosulabryum elegans, Rosulabryum erythroloma, Rosulabryum flaccidum, Rosulabryum gemmascens, Rosulabryum laevifilum, Rosulabryum pseudocapillare, Rosulabryum rubens, Rosulabryum torquescens

Key

1	Filiform gemmae present in distal leaf axils	> 2
1	Filiform gemmae absent or very rare	> 5
2	Innovations short, rosulate; leaves usually greater than 3 mm; margins strongly serrate distally, limbidium strong.	Rosulabryum andicola
2	Innovations short and rosulate or elongate and evenly foliate; leaves usually less than 2 mm; margins entire to serrulate distally, limbidium weak or absent	> 3
3	Innovations rosulate; leaves obovate, flat; filiform gemmae brown when mature.	Rosulabryum laevifilum
3	Innovations evenly foliate; leaves ovate to obovate, concave or flat; filiform gemmae red or brown	> 4
4	Rhizoidal tubers and filiform gemmae brown to red-brown, same color as rhizoids.	Rosulabryum flaccidum
4	Rhizoidal tubers orange, red, or pink, brighter than rhizoids, filiform gemmae red.	Rosulabryum pseudocapillare
5	Stems elongate, evenly foliate; leaves 3-4.5 mm; bases somewhat decurrent; margins sharply serrate distally.	Rosulabryum andersonii
5	Stems rosulate, or if evenly foliate then leaves less than 2 mm; bases decurrent or not; margins serrate to entire distally	> 6
6	Leaves usually 2-4 mm, often in interrupted tufts; margins distinctly and strongly serrate distally, limbidium strong to absent; costae short-excurrent; laminal cell walls porose	> 7
6	Leaves less than 2.5 mm, usually not in interrupted tufts; margins entire to serrate distally, limbidium present or rarely absent; costae not reaching apex to long-excurrent; laminal cell walls not or weakly porose	> 8
7	Limbidium strong; costal awns variously straight to curved when dry.	Rosulabryum andicola
7	Limbidium absent or weak; costal awns recurved when dry.	Rosulabryum canariense
8	Stems evenly foliate; leaves ± imbricate when dry; rhizoidal tubers very rare.	Rosulabryum elegans
8	Stems usually rosulate, although innovations sometimes evenly foliate; leaves usually contorted or twisted when dry, rarely innovation leaves imbricate; rhizoidal tubers often present	> 9
9	Plants maroon, red, or red-green; leaf bases decurrent; costae not reaching apex, percurrent, or short-excurrent.	Rosulabryum erythroloma
9	Plants green, brown, or red-green; leaf bases not decurrent; costae short- to long-excurrent, rarely not reaching apex	> 10
10	Sexual condition dioicous, synoicous, autoicous, or polyoicous; rhizoidal tubers amber, orange, orange-red, scarlet, crimson, or red, usually brighter than rhizoids; leaf margins distinctly serrate or serrulate distally; capsules often strongly nutant, red to red-brown	> 11
10	Sexual condition dioicous; rhizoidal tubers crimson, red, red-brown, or orange-red, usually same color as rhizoids, if brighter than either tubers distinctly warty with protuberant cells or leaf margins nearly entire distally; leaf margins entire to distinctly serrulate distally; capsules inclined to nutant, red to brown	> 12
11	Tubers orange to amber, becoming brown with age; leaves ovate; margins weakly serrulate distally, limbidium moderately distinct.	Rosulabryum bornholmense
11	Tubers scarlet, crimson, or red; leaves broadly ovate to obovate; margins strongly serrate distally, limbidium strong.	Rosulabryum torquescens
12	Rhizoidal tubers with strongly protuberant cells, crimson, red to dark red, on short rhizoids at base of stem; leaf margins distinctly serrulate distally; leaves irregularly contorted when dry.	Rosulabryum rubens
12	Rhizoidal tubers smooth or almost so, red-brown or brown, usually on long rhizoids away from stem base; leaf margins ± entire distally, if serrulate then leaves spirally twisted around stem when dry	> 13
13	Limbidium present, margins serrulate distally; innovations short, rosulate; rosette leaves spirally twisted around stem.	Rosulabryum capillare
13	Limbidium absent or weak, margins entire or weakly serrulate distally; innovations elongate, evenly foliate; rosette leaves irregularly twisted to contorted.	Rosulabryum gemmascens