Pointed Spear-moss

Ciarán Byrne @kiwibyrne  

This grows (abundantly) in my lawn and I've tried a couple of times before to identify it. The last time was probably February, which was probably the last time I'd got the moss book out. It was a eureka moment to finally pin it down but not before I'd arsed about in the acrocarp keys: what an idiot! It's a pleurocarp of course. That's what happens when you don't know what you're doing and you don't start at the beginning.
Anyway, having dissected it under the stereomicroscope and looked at the cellular structure of the leaf under the compound microscope, I could have identified it without either if I'd just followed the key.
It is Pointed Spear-moss, Calliergonella cuspidata. I've nicked the photo from Ciaran Byrne's twitter feed. Ciaran is an amazing ecologist and prolific tweeter. I would urge anyone with Twitter access to follow him.