Identification notes
Often, the first thing that attracts the roving bryologist to this delightfully neat cushion-former is its vivid green colour. This is of the same hue as its more common and spiky-looking sister P. hornschuchianum, although that species grows on the ground rather than the hard rock/masonry of P. revolutum. Both species like calcareous or base-rich substrates though.
Close examination of the cushions of tightly-packed shoots with a hand lens shows the leaf margins to appear strongly inrolled, a little like a Weissia. However, they are not inrolled or incurved at all. The margins are strongly revolute, so they turn down and curl inwards on the underside of the leaf, so much so that they obscure the nerve in the upper part. Leaves are small, but if you can manage to cross-section them with a sharp blade, the resultant section is at once striking and distinctive, like a scroll (there’s a good image of this below).
Read the Field Guide account