Barbula unguiculata

Found this on a wall in Inverkeithing harbour and was delighted to see the bearded capsules. Papillose and opaque, the small yellowish-green leaves have a strong nerve, slightly excurrent. By breathing into my hand while holding it I could see the beard extend, until I decided to go the whole hog and dunk it into a drop of water, upon which it fully extended - a superb way of controlling spore dispersal so that spores are only sent out into benign conditions.

Barbula factoids:
Barbula genus is in the Pottiales
Barbula of old has been largely split into Barbula, Didymodon and Pseudocrossidium genii
Barbula unguiculata has small (<2mm), papillose, opaque leaves with a strong, excurrent nerve
Barbula unguiculata leaves have revolute margins
Barbula unguiculata likes neutral-base habitats like path edges or old walls
Barbula unguiculata has a largely erect capsule on a red seta
Barbula convoluta has a more percurrent nerve, and leaves generally not exceeding 1.5mm
Barbula convoluta has less revolute leaf margins than unguiculata
Barbula sardoa is more robust and darker green than unguiculata and has wavy leaf margins