Grimmia pygmaea Mull. Hal.

11. Grimmia pygmaea Müll. Hal.

, Syn. Musc. Frond. 1: 787. 1849

(Fig. 13).

– Grimmia trichophylla var. australis Hampe in Syn. Musc. Frond. 1: 788. 1849. [nom. inval.].

Lectotypus (designated by Muñoz & Pando, 2000: 67): AuStrAliA: “Gr. trichoph.-australis Hamp. N. Holl.”, s.d., Anon. s.n. (H-SOL!).

5 Grimmia drakensbergensis Sim in Trans. Roy. Soc. South Africa 15: 209. 1926.

Typus: South AfriCA. Prov. Natal: Top of Giants Castle. 2440 m, 1912, Sim 9962 [leg. Symons s.n.] (holo-: PRE), synonymized by Maier (2010: 300).

Gametophyte. Monoicous. Female: innermost perichaetial leaf up to 2 mm long, sheathing, costa stout, percurrent, hair-point scarcely denticulate; male: perigonia in leaf axils or on short branches originating there, several on a stem, usually far from the perichaetium, innermost perigonial leaf 0.8 mm long, hyaline except the apical part, costa percurrent. Growth form: cushions adhering to the substrate by rhizoids or desintegrating, occasionally young shoots originating from the stem base, apices of the leaflets appressed to stem, plants erect, stems from 15 mm up to 70 mm high, branched by innovations, leaves arranged in tiers, stem with well-developed central strand. Leaves 1.5-2.5 mm long, densely set, in dry state appressed to stem, slightly turned, scarcely moving when moistened, erecto-patent when wet, from elongate-ovate leaf base lanceolate, tapering to acute apex, hair-point weakly denticulate; leaf form in situ, at base concave, lower laminal part keeled, upper part narrowly so, margins weakly recurved on both sides from above leaf base to upper part of lamina, apical part of lamina plane; basal cells elongate-rectangular, walls thickened, weakly to strongly nodulose, variable from leaf to leaf on the same plant, near margin two or three rows of shorter cells with smooth walls appearing hyaline and differentiated from the elongated nodulose basal cells, in transitional part lamina cells narrow, elongate-rectangular with mostly strongly sinuose walls becoming shorter towards the margin, in apical part cells isodiametric or short-rectangular, walls thickened, more or less sinuose; leaf base, seen in transverse section, unistratose, lamina mostly unistratose throughout, in rare cases with bistratose patches, margins unistratose in leaf base and lower half of lamina, in upper part of lamina one to three marginal rows bi- or even tristratose. Costa, seen on dorsal side, of nearly uniform width, slightly thinner in leaf base, percurrent, costa, seen in transverse section, dorsally rounded, from above insertion to below apical part the costa being prominent, in laminal part exterior walls of dorsal cells markedly thickened, on ventral side in basal part widely channelled, in laminal part channelled, at insertion and at leaf base with 4 guide cells, in laminal part 2 guide cells, in mid-leaf small and elliptic in shape, mostly obliquely arranged to leaf axis, in leaf base and laminal part a centrally arranged group of hydroids or only one big star-shaped hydroid, vanishing in apical part, the dorsal costal cells with a small rounded lumen, transformed to substereids or stereids in the lower part of the leaf, in the prominent part of the costa a series of stereids arranged around the hydroids.

Sporophyte. Seta to 2 mm long, arcuate or curved, vaginula 0.8 mm long, cylindrical. Capsule exserted, horizontal or slightly pendulose, obloid, ribbed, exothecial cells elongated, rectangular, penta- and hexagonal, walls thin, stomata numerous on short neck, annulus of 3 to 4 rows of cells detaching in fragments, cells at orifice of capsule with smooth, or rarely slightly crenulate outer walls. Calyptra mitrate, covering the upper third of capsule. Operculum conical with short beak, at rim some rows of cells with rounded lumina, in conical part rectangular or of irregular shape. Peristome teeth erect when dry, lanceolate, divided in the upper half into two divisions, the lower dorsal plates smooth, the subsequent plates with fine papillae, upper dorsal and ventral sides densely covered with rough papillae, trabeculae small to broad throughout, distant. Spores 11-15 µm, nearly smooth.

Diagnostic characters. – Gametophyte. Cells in leaf base elongate-rectangular with nodulose walls, lamina cells in transitional part elongate-rectangular with sinuose walls. Costa rounded except from above insertion up to below apical part where the costa is prominent and the exterior walls of dorsal cells are markedly thickened. In the same part, the guide cells are small and elliptic, mostly arranged obliquely to the leaf axis, whilst in the leaf base and laminal part a centrally arranged group of hydroids or one star-shaped hydroid can be observed, vanishing in the apical part.

Distribution, habitat and ecology. – Grimmia pygmaea is a south-temperate species, known from New Zealand, Australia, Patagonia, and the Kerguelen Islands.

In South Africa and Lesotho (Fig. 2 E) G. pygmaea is the most common species of Grimmia at high altitudes (>2,500 m) in the Drakensberg of Lesotho and adjacent South Africa, where it grows on basalt. Within the study area the vast majority of known populations are from this region. However, it is also known from a smattering of localities in the southern part of the Cape Fold Mountains, and from two intermediate stations along the Great Escarpment. In the western part of its range it mostly occurs on quartzitic sandstone at high altitude, but occasionally descends to near sea level (e.g. on the Cape Peninsula).

Notes. – A total of 79 specimens were seen for this study and 38 of these had sporophytes, of which 3 were in a suitable state for examination, 9 were immature and 27 were decomposed. This species has been misunderstood, and largely neglected. Specimens from the study area were almost invariably identified as G. pulvinata. Whilst the two species are superficially similar, the paracostal cell differences (elongate-rectangular and nodulose in G. pygmaea versus shorter and smooth-walled in G. pulvinata) are diagnostic. Furthermore, G. pulvinata is predominantly found at lower elevations (not known from> c. 1,900 m), whilst most collections of G. pygmaea are from higher altitudes, although in the Western Cape it can occur at much lower elevations. The costal anatomy will also readily distinguish G. pygmaea from both G. orbicularis (also superficially similar, but ecologically very different) and G. pulvinata.

Selected specimens examined. – leSotho: Mokhoapong Pass, along Mountain Road, 147 km E of Maseru, 2710 m, 30.XI.1977, Magill 4204 (BOL); Moseru District. Thaba-Putsoa (High Pass) on the road to Semonkong. 3090 m, 29°44’S 27°57’E, 20.IV.1994, Duckett & Matcham 1246a (herb. Matcham). South AfriCA. Prov. Natal: Drakensberg area, Umgatsheni valley between Sani Pass and Vergelegen, c. 2130 m, VII.1983, Esterhuysen 35934 (BOL); E. Cape, Lady Gray Distr., Witteberg, Joubert’s Pass, 2440 m, 18.I.1979, Hilliard & Burtt 12221 (BM).