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ANDREAEACEAE

(N.G. Hodgetts)

A monogeneric family in the class Andreaeopsida.

Andreaea Hedw.

Fourteen species are recorded from sub-Saharan Africa. There are about 50 species worldwide (Murray 1988). A key was provided to the costate species by Schultze-Motel (1970).

Plants mostly small to medium sized, forming readily-disintegrating tufts or mats, dark brown, reddish-brown or black, stem and branch tips green or yellowish green. Stems erect to somewhat spreading, few to several branched; in cross-section cells thick-walled, outer 2-4 rows of cells small, inner cells larger, central strand absent. Leaves loosely erect to appressed, occasionally contorted when dry, erect-spreading when wet, oblong-lanceolate to subulate, broadly oblong-ovate to panduriform, or broadly elliptical, to 3 mm long, concave, slightly clasping stem, often channeled above, apex narrowly to broadly acute or acuminate, or broadly obtuse and apiculate, base subauriculate or not; margins plane, erect to enrolled or reflexed to recurved, entire or crenulate by bulging cell walls; ecostate or costate, if costa present then single, either short and broad (1/2 or more leaf width at base) or filling acumen; laminal cells thick-walled, often sinuose and porose, upper and median cells ± hexagonal or quadrate to shortly rectangular, smooth to papillose; lower and basal cells shortly to longly rectangular. Autoicous or dioicous. Perichaetia terminal, leaves differentiated, large, 2 or more times longer than stem leaves, often sheathing the pseudopodium. Pseudopodium (seta-like structure) ± short to elongate, to 5 mm long. Capsule erect, ovoid to cylindrical, 0.5-2.0 mm long, splitting nearly the full length of the capsule by 4 slits or valves; true peristome and operculum absent. Calyptra mitrate-campanulate. Spores spherical, papillose.

Habitat. On acidic rocks, in open exposed sites or in streams; confined to montane areas, 1400-5000 m.

Discussion. Andreaea, a characteristic component of the tropical alpine life zone, is recognised by its black to reddish-black gametophytes, with costate or ecostate leaves exhibiting thick-walled and often sinuose laminal cells, which are frequently papillose on the distal abaxial surface; when fertile the pseudopodium and 4-valved capsule are diagnostic. Andreaea requires a critical revision in Africa: B. Murray is currently preparing a worldwide revision of the genus. Until this is available, useful references include Demaret (1943), De Sloover (1977), Hodgetts et al. (1999) and Magill (1981).

Literature. Demaret, F. 1943. Le genre Andreaea en Afrique centrale et orientale. Bulletin du Jardin Botanique de l'État à Bruxelles 17: 33-48. De Sloover, J.L. 1977. Note de bryologie africaine IX. Andreaea, Racomitrium, Gymnostomiella, Thuidium. Bulletin du Jardin Botanique National de Belgique 47: 155-181. Hodgetts, N.G., Matcham, H.W. & Duckett, J.G. 1999. Bryophytes collected in Lesotho, the Natal Drakensberg and the Orange Free State, southern Africa. Journal of Bryology 21: 133-155. Magill, R.E. 1981. - see general refs. Murray, B.M. 1988. The genus Andreaea in Britain and Ireland. Journal of Bryology 15: 17-82. Schultze-Motel, W. 1970. Monographie der Laubmoosgattung Andreaea. 1. Die costaten Arten. Willdenowia 6: 25-110.

uploaded 7.05.2005