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HEDWIGIACEAE

(B.J. O'Shea)

Plants medium sized, forming tufts or cushions, glaucous to dark green, brown to yellowish. Stems spreading to ascending or erect, several branched, weakly radiculose at base; central strand absent or weak; pseudoparaphyllia filamentous. Leaves imbricate, spirally arranged, appressed to erect when dry, spreading to wide-spreading or squarrose when wet, ovate, obovate, narrowly to broadly lanceolate or oblong-short lanceolate, apex acute to acuminate, hyaline or not; margins plane to recurved below or throughout, entire or dentate at apex, elimbate; costa none; laminal cells quadrate to short rectangular, papillose, walls sinuose; insertion cells elongate and sinuose, papillae in rows, often golden-brown. Autoicous, rarely synoicous or polyoicous. Perichaetia terminal but appearing lateral, leaves elongate, broadly to rather narrowly lanceolate, margins ciliate or not. Seta short or elongate, smooth. Capsule immersed or exserted, erect, short cylindrical to ellipsoid or subglobose, often striate or ribbed when dry. Operculum plano-mammillate to short rostrate. Peristome absent. Calyptra cucullate or short and mitrate. Spores spherical, papillose, rarely multicellular.

Discussion. The Hedwigiaceae contain four genera and about 20 species; in sub-Saharan Africa, three genera and ten species. The family is recognized by the ecostate leaves, papillose laminal cells that are sinuose, and capsules that lack a peristome. Rhacocarpus was in the past placed in the Hedwigiaceae but is now placed in its own family, the Rhacocarpaceae; see discussion and review by De Luna (1990b).

Literature. De Luna, E. 1990a. Developmental evidence of acrocarpy in Hedwigia ciliata (Musci: Hedwigiaceae). Tropical Bryology 2: 53-60. De Luna, E. 1990b. Protonemal development in the Hedwigiaceae (Musci), and its systematic significance. Systematic Botany 15: 192-204. De Luna, E. 1992. Developmental and systematic studies in the Hedwigiaceae (Musci). Ph.D. thesis. Ann Arbor: University Microfilms International. De Luna, E. 1995. The circumscription and phylogenetic relationships of the Hedwigiaceae. Systematic Botany 20: 347-373.

Braunia Bruch, Schimp. & W.Gümbel

Eight species and one variety are recorded for Africa, although this number may be reduced to seven (De Luna 1992) following revision; a genus containing 16 species.

Plants medium sized, forming loose to dense coarse mats or tufts, dull yellowish-brown to golden. Stems creeping, leaves mostly reduced, scale-like, appressed with tips spreading to recurved, frequently eroded from stem, distal stems and branches mostly ascending, several branched; pseudoparaphyllia foliose. Leaves imbricate, appressed with apices reflexed when dry, erect-spreading to spreading or squarrose when wet, ovate, obovate to oblong-ovate or lanceolate, 1.5-2.0 mm long, flat to concave, weakly to strongly plicate, apex short acuminate to abruptly long acuminate; margins entire below, apices irregularly dentate, erect to recurved throughout or partially, rarely plane; laminal cells thick-walled, upper and median cells short to long and narrowly rectangular, ± sinuose, papillose; lower middle and basal cells long rectangular, sinuose, papillose, papillae in single row; alar region differentiated, subquadrate to short-rectangular and oblate, walls rounded. Synoicous. Perichaetia appearing lateral, leaves elongate, narrowly- oblong-lanceolate. Seta elongate, (3-)5-18 mm long, smooth, often twisted. Capsule exserted or emergent, erect to suberect, urn ovoid, cylindrical or ellipsoid to subglobose, 1.3-2.2 mm long, wrinkled or furrowed when dry, mouth slightly constricted. Operculum long rostrate, oblique. Peristome absent. Calyptra cucullate, smooth and naked. Spores spherical or multicellular, papillose.

Habitat. Epiphytic on tree trunks or branches, and on rocks; open to forested montane to alpine, (500-)1350-3500 m.

Discussion. Braunia is readily distinguished from the two remaining genera of the family by the elongate seta and well exserted capsule. In the absence of sporophytes, however, the genera are difficult to distinguish, particularly Braunia and Hedwigidium. Braunia is found on rocks as well as shrubs and trees, whereas Hedwigia and Hedwigidium are almost always restricted to rocks. De Luna's thesis (1992) has not resulted in any taxonomic publications regarding African Braunia, although many herbarium specimens show his annotations. The most commonly reported species in Africa (B. secunda) is said by De Luna (1992) to be exclusively American, so much African material will need to be re-identified.

Literature. De Luna, E. 1992. - see family ref.

Hedwigia P.Beauv.

A single species in the area, H. ciliata (Hedw.) Ehrh. ex P.Beauv., with varieties ciliata (Cape Verde Islands, DR Congo (Zaire), East and Southern Africa and Madgascar) and leucophaea Bruch Schimp. & W.Gümbel (East Africa); the genus contains three or four species.

Plants medium sized, forming loose to dense tufts or cushions, grayish-green. Stems spreading to suberect; pseudoparaphyllia filamentous. Leaves appressed to erect when dry with distal apices spreading or recurved, spreading to erect-spreading when wet, ovate-lanceolate, 2.0-2.3 mm long, apex acuminate, upper 1/4 of apices hyaline and distinctly papillose; margins plane or slightly recurved below; costa absent; apical cells elongate, hyaline and indistinct, papillae in single row, to 8 or more; median cells short rectangular or quadrate, appearing sinuose, papillose, papillae 1-3, simple or branched; upper basal centre cells long rectangular, papillae 3-6; lower basal centre and insertion cells smooth, porose, often golden-brown. Perigonia bud-like, appearing lateral. Perichaetia on short terminal branches, appearing lateral, leaves narrowly lanceolate, distal margins long ciliate, cilia long and short branched, hyaline. Seta very short, 0.25-0.50 mm long, smooth. Capsule immersed, erect, urn short cylindrical, subglobose when deoperculate, 1.0-1.2 mm long, smooth. Operculum plano-mammillate. Peristome absent. Calyptra small, mitrate, smooth and hairy. Spores with trilete lines, coarsely rugose-papillose.

Habitat. On rocks, very occasionally reported from tree bases; open montane to alpine areas, (500-)1800-3700 m.

Discussion. The hyaline leaf tips, ciliate margins of the perichaetial leaves, and immersed and rather smooth capsules, in combination with the shared family features, distinguishes Hedwigia.

Hedwigidium Bruch, Schimp. & W.Gümbel

A monotypic genus represented by H. integrifolium (P.Beauv.) Dixon in C.E.O.Jensen, found in our area in Cameroon, East and Southern Africa and Réunion. (also Western Europe, pantropical at high elevations, Australia and New Zealand).

Plants medium sized, forming tufts or mats, green to dark reddish-brown. Stems erect or spreading; central strand absent; pseudoparaphyllia foliose. Leaves appressed, spreading to wide-spreading when wet, ovate to oblong-ovate, 1.5-2.2 mm long, weakly plicate or not, apex acute or short acuminate; margins strongly recurved, entire below, distally dentate or crenulate, occasionally weakly toothed; costa absent; apical cells elongate, median cells short rectangular to subquadrate, sinuose, papillose, papillae several along margin, appearing over lumen; central upper basal cells rectangular, porose, papillae few to several (7 or more) in single row (rarely double row); insertion cells at center smooth, golden-brown or yellow; cells of alar region quadrate, smooth. Perichaetia appearing lateral, but on terminal branches, leaves broadly lanceolate to oblong-lanceolate, to 5 mm long, plicate, short acuminate, upper margins not ciliate. Seta short, 0.8-1.2 mm long. Capsule immersed, erect, short obloid, 1-2 mm long, furrowed when dry or wet. Operculum short rostrate, oblique. Peristome absent. Calyptra small mitrate, smooth and naked. Spores with trilete lines, rugose-papillose.

Habitat. On rocks; open montane to alpine, 1600--3900 m.

Discussion. The genus is characterized by the concolorous leaves, elongate, eciliate perichaetial leaves, furrowed and immersed capsules. Without sporophytes, H. integrifolium is difficult to distinguish from Braunia growing on rock, so always look carefully for sporophytes (which are quite often present).

accepted 11.05.2000