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GIGASPERMACEAE

(R.E. Magill)

Plants small, scattered and gregarious, glaucous green to light or dark green. Stems arising from a long aphyllous rhizome; in section with central strand weak or absent. Leaves appressed or erect spreading, concave, broader above, orbicular to broadly elliptical or obovate; apex rounded and abruptly apiculate or awned; margins plane and entire; costa absent or if present, short or long excurrent; leaf cells small, smooth, angular or quadrate to hexagonal; thin walled. Gemmae uncommon at leaf apex, lenticular. Autoicous or dioicous with dwarf males. Perichaetia terminal, leaves somewhat distinct, larger. Seta very short or elongate. Capsule immersed or exserted, cleistocarpic and subspherical or stegocarpic, gymnostomous, cupulate to short cylindrical; exothecial cells lax; stomata present at base of urn. Operculum plano-convex, apiculate. Calyptra very small. Spores large, granulate, reddish brown.

Discussion. The Gigaspermaceae contain 4 genera, only the American genus Lorentziella not known from Africa. The other three genera are restricted to the dry shrublands of southern Africa; Oedipodiella has been reported from Europe and Gigaspermum from Australia and New Zealand. Gigaspermum and Chamaebryum both exhibit short, bulb-shaped gametophytes scattered on relatively open soil. The exposed plants arise from a long creeping rhizome that lies just below the surface or is closely appressed to rock in more exposed area. The plants are most often collected along small, dry water courses or on soil crusts under short shrubs. Oedipodiella is found on soil in wooded canyons in savanna habitats.

Literature. Magill, R. E. 1987. Flora of Southern Africa. Part 1. Mosses. Fascicle 2: 299-303.

 

1. Leaves ecostate Gigaspermum
1. Leaves costate 2
2. Costae long excurrent as smooth, hyaline awn; capsules exserted Chamaebryum
2. Costae cuspidate or short excurrent, green; capsules immersed Oedipodiella

Chamaebryum Thér. & Dixon

One species endemic to southern Africa, C. pottioides Thér. & Dixon.

Plants small, light green, caespitose. Stems erect, 2-6 mm high from a highly branched, creeping rhizome; central strand absent. Leaves crowded above, obovate to orbicular, 0.8-1.2 mm long; apex obtuse, cuspidate to piliferous; costa percurrent in lower leaves, short or long excurrent in upper leaves forming smooth, hyaline awn, to 0.5 mm long; leaf cells angular to quadrate, basal cells short rectangular. Gemmae rare, at apex of sterile plants, bulging lenticular, to 0.2 mm long, with pronounced, hyaline, distal apiculus, cells hexagonal. Monoicous. Perichaetia terminal, leaves somewhat larger. Seta erect, 0.6-1.8 mm long. Capsule exserted, gymnostomous, short cylindrical, 1.0-1.3 mm long, mouth narrow; exothecial cells lax, subhexagonal. Operculum remaining attached to columella when capsule first opens. Spores round, 50-55 µm.

Habitat. The genus is endemic to dry, rocky areas of southern Africa.

Discussion. The creeping rhizome, concave and piliferous leaves, and exserted, small mouthed capsule will serve to identify this taxon. The plants frequently have a greyish colouration when dry much like some Grimmias, but Chamaebryum occupies a different habitat and the size and habit are quite distinct.

Literature. Magill, R. E. 1987. - see family ref.




Gigaspermum Lindb.

One species found in southern Africa, G. repens (Hook.) Lindb.

Plants small, light green or glaucous, scattered or loosely caespitose. Stems erect, 2--5 mm high, from a creeping, aphyllous rhizome; central strand weak. Leaves distant, erect-spreading, orbicular, apiculate, 0.5-0.8 mm long; ecostate; leaf cells quadrate to subhexagonal, smooth. Autoicous. Perichaetia terminal; leaves differentiated, elliptical and long acuminate, 2.0-2.5 mm long. Seta very short, 0.3-0.5 mm long. Capsule immersed, gymnostomous, cupulate, 0.8-1.0 mm long; mouth very broad; exothecial cells lax, quadrate to hexagonal. Calyptra small, campanulate. Spores round to angular, 80-100 µm.

Habitat. On poor, rocky soils in open shrublands of the desert southwest, but should be expected in grasslands and shrublands of northern Africa.

Discussion. Scattered, sterile plants are difficult to detect, but the larger perichaetial leaves and wide-mouthed capsules with red-brown spores make the plants more obvious. The short and broad, ecostate leaves will also help to identify this taxon.

Literature. Magill, R. E., 1987. - see family ref.




Oedipodiella Dixon

One species in Africa, O. australis (Wager & Dixon) Dixon.

Plants small to medium sized, scattered or in loose cushions, dark green. Stems erect, 2-5 mm long from branching, aphyllous rhizome; central strand absent or not well defined. Leaves crowded above, wide spreading, obovate to spathulate or broadly elliptical, 2-4 mm long; apex rounded and abruptly apiculate; costae short excurrent; leaf cells subquadrate to hexagonal, basal cells longer, short rectangular. Gemmae at stem apex, lenticular, 0.3-0.6 mm across. cells quadrate to short rectangular. Dioicous. Perichaetia terminal; leaves spathulate to lingulate, 3.0-3.5 mm long; apex rounded, apiculate; costae ending below apex. Seta very short. Capsules immersed, cleistocarpic, subglobose, beaked, 1.0-1.5 mm long; exothecial cells lax, quadrate to subhexagonal. Spores round, 45-50 µm.

Habitat. On soil in wooded areas of otherwise open grasslands.

Discussion. The plants have an appearance of some broad-leaved Pottiaceae, but the frequently produced, lens-shaped gemmae will help to place Oedipodiella. The small, immersed, subglobose, cleistocarpic capsules and branching rhizome will also be useful in identifying this genus.

Literature. Magill, R. E. 1987. - see family ref.

 


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accepted 11.06.2003