Seaside Grimmia

Schistidium maritimum is one of the easiest species of the genus to identify. Its usually 2-stratose distal laminae, well developed stereid bands, usually small and often campanulate capsules, and coastal habitat are distinctive. Subspecies piliferum, characterized by the presence of awns and a single stereid layer, is not recognized here; further study is needed.

Plants in tufts, olivaceous, often brownish. Stems 0.8-5 cm, central strand absent. Leaves usually curved, sometimes erect, often somewhat contorted when dry, ovate-lanceolate to linear-lanceolate, keeled, (1.2-)1.5-2.6(-4) mm, usually 2-stratose distally; margins usually plane distally, recurved proximally, smooth or papillose, 2-stratose or 3-stratose, rarely 4-stratose distally; apices acute or blunt, sometimes ending in a short, fleshy, multistratose apiculus; costa percurrent, rarely excurrent as a short denticulate awn, with guide cells and one or two stereid bands, abaxial surface usually slightly papillose; basal marginal cells quadrate or short-rectangular, often trigonous; distal laminal cells isodiametric, rounded or angular, sometimes short-rectangular, 7-11 µm wide, smooth or weakly papillose, sometimes weakly bulging-mammillose, straight or slightly sinuose. Sexual condition autoicous. Capsule dark reddish brown or dark brown, ovoid, cupulate, or campanulate, 0.6-1.3 mm; exothecial cells usually angular, isodiametric, occasionally elongate, thick-walled; stomata present; peristome patent to revolute, 200-500 µm, red, papillose, often strongly perforated. Spores 15-30 µm, granulose.

Grimmia maritima Turner ex Robt. Scott, Trans. Dublin Soc. 3: 158, plate 1. 1803; Schistidium maritimum subsp. piliferum (I. Hagen) B. Bremer

Grows on maritime sea shores in small rock crevices just above high-water level and it is often covered with salt spray. It is one of "extremely few obligate bryophyte halophytes" (Richards 1932: 384) and according to him it never grows in inland habitats. In S there are two specimens from Lake Ontario collected by Macoun. If these are correctly labelled, they must have been growing in inland habitats probably near fresh water. Possibly they are relicts from earlier periods when this lake held saline water (Foster Flint 1957). In cultivation, S. maritimum grows well without saline water and salt spray.