I have had this moss growing on my garage roof for years, and it has virtually covered all of it. It shrivels up to a brown crisp in very dry weather, and yet as soon as a drop of rain falls it immediately expands like a sponge and greens up.
A dull green to golden green moss which grows in tufts or loose cushions. The stems grow to a height of 1 to 4cm. The leaves are about 4mm long and are slightly narrowed at the halfway point, the lower margin having recurved margins. The tip is rounded and flat. The leaves spread out widely from the stem when wet, and when dry they are spirally twisted or incurved. Dry leaves may also appear pointed, making them seem tapered at the tip instead of rounded. The reddish-brown nerve projects from the leaf tip into a long, silvery white hair point which has small, coarse teeth. The capsules are cylindrical and erect, ripening to a reddish-brown colour. They appear in spring and summer, and are frequent.
Found on calcareous substrates such as roofs, calcareous rocks and walls. Also found on sunny, exposed stony ground. Common and widespread in most of lowland Britain, scarcer elsewhere.