Family: Grimmiaceae; Order: Grimmiales(de)
The genus Grimmia, whose members can be found worldwide, consists of about 150 species, of which 30 can be found in Europe. It is the most numerous genus of the family. All its plants form dense cushions of short, erect stems. Normally they prefer bright, exposed locations on rock. Some species can stand extreme drought. In the mountains Grimmia species grow at the borders of plant life.
The leaves are always lanceolate. In most cases they have a hyaline tip or hair. The upper cells are rounded quadratic, the lower cells elongated rectangular. In contrast to the genera Racomitrium and Dryptodon the cell walls are never are knotty like barbed wire. Often the blase is bistromatic (two cell layers thick).
The capsula sit on a short, sometimes straight, sometimes arcuate seta, and are raised a little bit over the cushion. The calyptra is hood-shaped.
Grimmia pulvinata is one of the most frequent mosses in cities. It grows in compact, blackish-green or grey cushions on walls, and can be found nearly everywhere without any problems. But also out the towns it is rather frequent on sunny rocks. It prefers basic rock as e.g. cement or concrete.
The lanceolate leaves end in long, hyaline tips, which can easily be seen with the naked eye, and give the cushions their characteristical grey habit.