Grimmia donniana Sm.

Gametophyte. Monoicous. Female: innermost perichaetial leaf to 2.5 mm long, sheathing to mid-leaf, not very different from stem leaves in shape and cell pattern, lower part of leaf hyaline, costa percurrent, hair-point long, denticulate; male: Perigonia on short subperichaetial branches as buds on short stalks in leaf axils, innermost perigonial leaf 0.8 mm long, sheathing to broadest part, ovate, obtuse or mucronate, muticous or with acute hyaline end cell, in lower part or from base to below leaf tip hyaline, costa weak, percurrent, antheridia with few paraphyses. Growth form: dense, compact cushions, adherent to substrate by rhizoids, young shoots originating from rhizoids or older stem parts, leaflets muticous, apex acute, stems to 20 mm long, plants erect, branched, radiculose at base, central strand developed. Leaves in lower part of stem small, muticous, in upper part to 2.4 mm long, loosely arranged on stem, apices slightly bent towards stem when dry, longer leaves bending backwards, shorter leaves moving slightly when moistened, erectopatent when wet, from narrow base elongate-lanceolate, tapering to rounded or obtuse apex, hair-point elongate, smoothly denticulate; leaf form in situ, at insertion and in leaf base concave, lower laminal part keeled, upper part narrowly so, margins plane throughout; basal paracostal cells elongate-rectangular, walls smooth, towards margin some rows of elongate-rectangular, hyaline cells present, longitudinal and transverse walls evenly thin, smooth, the rows gradually vanishing, outermost row reaching to above broadest part of leaf, thus forming a delimitation between hyaline and thicker walled chlorophyllose cells running obliquely from costa to margin, cells in transitional part near costa rectangular, walls sinuose, towards margin some hyaline cells with finely sinuose walls, lower lamina cells short-rectangular, walls more or less sinuose, thickened, in upper laminal part cells mostly isodiametric, walls thickened, smooth or sinuose; seen in transverse section, lamina unistratose or bistratose in places, occasionally totally bistratose, margin unistratose in leaf base, in laminal part several rows bi-or tristratose. Costa, seen on dorsal side, small in leaf base, becoming gradually broader in laminal part, indistinct at apex, percurrent or excurrent, seen in transverse section, on dorsal side at insertion and in leaf base angulate or rounded, in laminal part rounded or occasionally prominent, on ventral side at insertion nearly plane, in leaf base widely channelled, in lower part of lamina channelled, in upper part narrowly so, at insertion and in leaf base 4 guide cells, from transitional part to apical part 2 guide cells, from insertion to upper laminal part a median group of hydroids, at insertion and in leaf base costal cells substereid. Sporophyte. Seta of different lengths, 0.8-3.0 mm long, straight, occasionally curved, vaginula 0.8 mm long, cylindrical, ochrea broad. Capsule erect, horizontal at curved seta, ovoid, smooth, bright-coloured when mature, with age turning brownish, exothecial cells irregular, quadrate, hexagonal, elongate, thin-walled, seen in transverse section of capsule, exterior walls smooth, stomata large above capsule base, neck lacking, annulus of 2 rows of cells, if detaching then singly, seen in surface view cells round with small lumina. Calyptra mitrate, lobed, covering operculum. Operculum conical, mammillate, base smooth, cells rounded, thick-walled. Peristome teeth incurved or recurved when dry, broad at base, mostly entire at apex, separated down to insertion or at least to the lower most plates, dorsal side in lower half covered with minute papillae, upper half of dorsal side and ventral side densely covered with fine papillae, trabeculae small, close together or distant, prominent in lower half, scarcely marked in upper part. Spores 8-9 µm, smooth.