Racomitrium crumianum

Detailed description

Saxicolous, yellowish or brownish-green tufted moss inhabiting moist granite. Stems up to 20 mm long, weakly creeping or upright, sparsely branched near base, reddish-brown, in cross-section more or less triangular, lacking a central strand, with firm-walled cells surrounded by 2-4 layers of isodiametric, very incrassate cortical cells. leaves imbricate and fragile, c.3 mm long, lanceolate, lacking a hair point, with apices nearly always broken, when dry with lower portions erect and the upper portions strongly circinate-reflexed, when moist erect-spreading and more or less straight, carinate throughout with a single plica extending from base well into the apex; margins strongly reflexed on one side, plane or nearly so on the other; nerve c.20 microns wide at base ending in acumen, in cross-section of 2 layers of cells throughout; lamina unistratose; cells thick-walled, smooth, and strongly nodulose throughout (except within 100 microns of apex), in lower portion of lamina very elongate, c.45-65 x c.6 microns, in median portion of lamina 18-30 microns long, and in uppermost fragile portion of leaf c.9-15 microns and quadrate to shortly rectangular; alar cells weakly differentiated, shorter, less nodose and more pigmented than adjacent laminal cells; marginal cells at base smooth-walled and forming a distinct border c.15 cells high; marginal cells in upper half of leaf longer than adjacent laminal cells, with incrassate, smooth walls and forming a distinct, uniseriate or biseriate, mostly unistratose border which extends to the leaf apex. Axillary hairs c.105 microns (6 cells) long (seemingly one in each alar angle). Sex organs and sporophyte not seen.