Sphagnum (bog moss) spore capsules

I don't often find spore capsules on bog moss Sphagnum species but they are well worth looking out for because they have a remarkable way of discharging their spores. 

They look like chestnut brown spheres, that swell and darken as they age.

When they mature you can see the lid. At this stage they remind me of tiny ginger jars. Gas pressure builds up inside as they age, and when the wall begins to dry out it shrinks. Eventually the pressure within  becomes so great that the capsule explodes, blowing the lid off and sending a column of spores into the air.

You can watch a video of this explosive 'air gun' mechanism  by clicking here