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RHABDOWEISIACEAE

(J.-P. Frahm)

Plants very small to medium sized, forming short tufts. Stems short, simple or few branched by innovations, with a central strand. Leaves mostly progressively larger distally, lanceolate to narrowly lanceolate or subulate from an oblong or oblong-ovate base; margins plane or recurved, entire or distal tips serrulate; costa single, subpercurrent to short excurrent; laminal cells smooth. Asexual structures absent. Autoicous. Sporophytes terminal; perichaetial leaves often larger and longer than stem leaves. Seta short to elongate, erect or curved to flexuose, smooth. Capsule immersed to exserted, urn obloid to pyriform with a neck distinctly elongate, occasionally as long as or much longer than the urn; stomata numerous in neck region, superficial; annulus often well developed. Operculum absent or present and rostrate. Peristome absent or single with 16 teeth. Calyptra cucullate or mitrate. Spores variously ornamented.

Discussion. The Rhabdoweisiaceae, although introduced by Limpricht in 1890, were usually included as a subfamily in the Dicranaceae. Recent molecular-systematic studies (Stech 1999) support the maintenance of Limpricht's concept. Limpricht included Cynodontium, Dichodontium, Oreas, Oreoweisia, Rhabdoweisia and Amphidium in this family, of which all genera except for Dichodontium and Oreas occur in tropical Africa.

Literature. Stech, M. 1999. A reclassification of Dicranaceae (Bryopsida) based on non-coding cpDNA sequence data. Journal of the Hattori Botanical Laboratory 86: 137-160.

Amphidium Schimp.

A genus of 11 species worldwide, of which 4 occur in the mountains of tropical Africa. Three species are known only from a small range, of which A. aloysii-sabaudiae G.Negri and A. le-testui Thér. are African endemics with very few collections and A. lapponicum (Hedw.) Schimp. is a mainly holarctic species which occurs also in southern Africa. Only A. tortuosum (Hornsch.) H.Rob. is more widespread.

Plants in small to tall, often large tufts, yellowish to olive green, rusty brown below. Stems erect, simple or rarely branched, moderately radiculose. Leaves crispate when dry, erect-spreading when wet, narrow-lanceolate, apex acute, concave; margins plane, smooth; costa percurrent; upper laminal cells irregularly subquadrate, polygonal or rounded, densely papillose on both surfaces, moderately incrassate, chlorophyllose, basal laminal cells lax, thin-walled, hyaline, elongate rectangular; alar cells not differentiated. Autoicous. Perichaetia terminal, perichaetial leaves longer, sheathing. Seta short, a few mm long, straight, twisted when dry. Capsule usually immersed in the perichaetial leaves or only shortly exserted, erect, pear shaped, with 8 distinct, darker coloured longitudinal ribs, widened at mouth when emptied. Operculum from flat convex base obliquely rostrate. Calyptra cucullate, smooth, entire at base. Peristome lacking. Spores verrucose, 20-25 µm.

Habitat. On rocks and in fissures of rocks in high montane to alpine regions, 2400–4800 m.

Discussion. Until recently, the systematic position of this genus was controversial, as the genus lacks peristome teeth and it could not be decided whether it was a haplolepidous or diplolepidous genus. According to gametophytic characters, it was either included in the Orthotrichaceae or Dicranaceae. Recent molecular systematic studies (Goffinet & Vitt, 1998; Stech, 1999) revealed that Amphidium is not a diplolepidous moss and does not fit into the Orthotrichaceae. It is now placed into the Rhabdoweisiaceae because of morphological and anatomical similarities with the other genera of this family. The two southern African species are well illustrated by Van Rooy (1991).

Literature. Goffinet, B. & Vitt, D.H. 1998. Revised generic classification of the Orthotrichaceae based on molecular phylogeny and comparative morphology. In Bates, J.W., Ashton, N.W. & Duckett, J.G. (eds.) Bryology for the twenty-first century: 143-159. Leeds: Maney Publishing and the British Bryological Society. Stech, M. 1999. A molecular systematic contribution to the position of Amphidium Schimp. (Rhabdoweisiaceae, Bryopsida). Nova Hedwigia 68: 291-300. Van Rooy, J. 1991. The genus Amphidium Schimp. in southern Africa. Lindbergia 17: 59-63.

Cynodontium Schimp.

A genus of about 10 species primarily distributed in the Northern Hemisphere. Only C. tanganyikae P.de la Varde has been recorded from tropical Africa.

Plants in small tufts, green to yellowish green. Stems to 3 cm tall, simple or rarely branched, whitish radiculose below. Leaves crispate when dry, erect-spreading when wet, linear-lanceolate, 4-5 mm long, apex acute, concave; margins partially recurved in the lower part of the leaf, weakly dentate in the upper part; costa subpercurrent, 1/4-1/5 width of leaf base; upper laminal cells irregularly subquadrate, mamillose, basal laminal cells lax, translucent, shortly rectangular, narrower at margins; alar cells not differentiated. Autoicous. Perichaetia terminal, perichaetial leaves ecostate, truncate, smooth. Seta 3-7 mm long, straight to curved or cygneous (when wet), smooth. Capsule erect to suberect, urn obovoid-cylindrical, 2.4 mm long, strongly furrowed when dry; annulus absent. Operculum conic-long rostrate, erect or oblique. Calyptra cucullate, smooth, entire at base. Peristome teeth golden, to 1/2-2/3 divided, vertically striate. Spores verrucose, 20--25 µm.

Habitat. Below a Philippia-shrub, only known from the type locality at Kilimanjaro Mtn., 4000 m.

Discussion. Potier de la Varde (1955) compares the only African species with C. fallax, from which it can be distinguished by a longer seta, ecostate perichaetial leaves and deeply furrowed capsule.

Literature. Potier de la Varde, R. 1955. Mousses récoltées par M. le Dr. Olov Hedberg en Afrique centrale, au course de la mission suédoise de 1948. Arkiv för Botanik 2,3: 124-204.

Oreoweisia (Bruch, Schimp. & W.Gümbel) De Not.

A genus of 15 species worldwide, which are characteristic for tropical mountains, especially the Andes. Only O. erosa (Müll.Hal.) Kindb. occurs in Central and Southern Africa, which is also widespread in the Andes from Mexico to Bolivia (Griffin, 1989).

Plants in loose tufts, green to yellow green. Stems erect, to 1 cm tall, radiculose below; in cross-section with central strand. Leaves crispate when dry,, loosely erect-patent when moist, ligulate, ca. 1.5-2 mm long, apex obtuse, rarely acute to rounded acute; margins recurved, erose-serrate in the upper part; costa strong, ending just below apex, ca. 1/5 width of leaf base, prominent on back; upper laminal cells short irregular, highly mammillose on both sides, basal laminal cells short rectangular, smooth, hyaline; alar cells lacking. Autoicous. Perichaetia appearing lateral, Perigonia terminal, leaves with clasping base. Seta 5-6 mm long, erect. Capsule erect, urn short cylindrical, 1.5 mm long; annulus persistent. Operculum conical, erect or somewhat oblique. Peristome teeth irregularly perforated, smooth. Calyptra cucullate, smooth, base mostly entire. Spores coarsely papillose, 20-22 µm.

Habitat. Terricolous.

Discussion. The genus resembles Rhabdoweisia with which it is placed in the same subfamily. The latter differs, however, by the 8-ribbed capsule and absence of a stem central strand.

Literature. De Sloover, J.L. 1975. Note de bryologie africaine. II. Oreoweisia, Eriopus, Cyclodictyon, Hookeriopsis, Lepidopilidium, Lepidopilum. Bulletin du Jardin Botanique National de Belgique 45: 103-124. [description, illustration]. Griffin, D. 1989. Oreoweisia erosa (C. Muell.) Kindb., an African-neotropical disjunct. Cryptogamie. Bryologie, Lichénologie 10: 297-300. [description]. Magill, R.E. 1981. - see general ref. [description, illustration].

Rhabdoweisia Bruch, Schimp. & W.Gümbel

Nine species worldwide, mainly in the northern hemisphere. Four species occur in Africa south of the Sahara, of which R. crispata (Dicks.) Lindb. and R. fugax Bruch, Schimp. & W.Gümbel are mainly holarctic species with disjunct occurrence in Southern Africa; R. africana Dixon & Naveau and R. lineata P.W.Richards & Argent are endemics in tropical Africa. All taxa except R. crispata are discussed briefly and partly illustrated by De Sloover (1973).

Plants small, in short dense or loose short tufts, green. Stems erect, to ca. 10 mm, little branched; central strand absent. Leaves crispate when dry, erect patent when moist, linear-lanceolate to oblong-lanceolate, 2-3 mm long, apex acuminate to obtuse; margins plane, entire to irregular denticulate or serrate at leaf tips; costa ending shortly below apex, filling 1/5 of leaf base; upper laminal cells quadrate-rounded, smooth; basal laminal cells elongate, lax and translucent; alar cells not differentiated. Autoicous. Perichaetia terminal, leaves similar to stem leaves. Seta short to elongate, 2.5-5.0 mm long. Capsule erect, urn ovoid to short cylindrical, to 1 mm long, distinctly ribbed when dry; annulus absent or weakly differentiated and persistent. Operculum short rostrate, oblique. Peristome reduced, teeth smooth or striate, undivided. Calyptra cucullate, smooth at base. Spores lightly to rather coarsely papillose.

Habitat. On rock and in rock crevices in montane regions.

Discussion. This genus differs from Cynodontium and Oreoweisia in its reduced peristome and capsules with 8 ribs; Amphidium is distinguished by its lack of a peristome.

Literature. De Sloover, J.L. 1973. Note de bryologie africaine. I. Brachydontium, Atractylocarpus, Amphidium, Rhabdoweisia, Tayloria, Rhacocarpus, Trachypodopsis. Bulletin du Jardin Botanique National de Belgique 43: 333-348.

accepted 04.05.2000