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AULACOMNIACEAE

(B.J. O'Shea)

A monotypic family.

Aulacomnium Schwaegr.

Probably only two species in our area: A. palustre (Hedw.) Schwägr. from Ethiopia, Kenya and Uganda, and A. turgidum Wahlenb. from Kenya; a mostly north temperate genus of seven species.

Plants medium sized to somewhat large, forming loose to dense tufts, yellowish-green or -brown. Stems erect, few branched, densely tomentose, very finely papillose/punctate; in cross-section central strand present. Leaves imbricate to contorted and twisted when dry, erect-spreading when wet, narrowly lanceolate to oblong-lanceolate to obovate, 4-5.2 mm long, to 1 mm wide, apex short acuminate or acute to obtuse, base weakly decurrent; margins recurved, crenulate and distally serrulate to entire; costa single, strong, very finely papillose/punctate on both surfaces, ending below apex, flexuose; basal cells inflated, 2-3-stratose, thick-walled, reddish-brown; median cells rounded, rounded-hexagonal or quadrate, lumens rounded to ± stellate and collenchymatous, unipapillose, papillae over cell lumen, to not or scarcely papillose. Propagula often present, clustered terminally on nearly naked elongate stems with a few scale-like leaves. Dioicous. [Sporophytes terminal. Seta elongate, 25-40 mm long, smooth. Capsule inclined to horizontal, urn oblong or ovoid-cylindrical, 2.5-4 mm long, asymmetric and curved, plicate and constricted below urn mouth when dry; annulus revoluble. Operculum conic to short-rostrate and oblique. Peristome double, exostome teeth 16, papillose, endostome basal membrane high, segments 16, keeled and perforate, cilia 2-4 . Calyptra cucullate, naked and smooth. Spores spherical, smooth.]

Habitat. Boggy or moist gound, or on wet rocks, 3600-4500 m.

Discussion. This genus is characterized by the recurved leaf margins, stellate and papillose or rounded and smooth laminal cells, reddish-brown, thick-walled, enlarged basal cells. All species of Aulacomnium examined (5 species) were found by H.W. Matcham (pers. comm.) to exhibit very finely papillose or punctate cells on the stem cortex and on both dorsal and ventral surfaces of the costa. This appears to be a character unique to the family. Sporophytes have not been reported from Africa, and are comparatively rare worldwide. Aulacomnium abyssinicum Schimp. ex Paris, nom. nud., reported for Ethiopia, is likely to be a synonym of A. palustre. Aulacomnium turgidum has leaves imbricate when dry, ovate to obovate, almost smooth laminal cells with star-shaped lumens, whereas A. palustre has leaves usually crisped or twisted when dry, more or less lanceolate, with more strongly papillose cells with rounded lumens.