Under dry conditions, the liverwort capsule splits into valves or segments, exposing the spores and elaters. Two forces are key here - cohesion between water molecules and adhesion between water molecules and the elater wall. Under dry conditions water is lost and the elater walls are pulled inwards. The elater walls have spiral bands of thickening so that as more water is lost the elaters assume a twisted form. The water is in a state of tension.
More water is lost.
This shifts the balance. The attractive forces between the water and elater are overcome. The elater snaps violently back to its original shape. The water remains as a cohesive mass. Cephalozia is an extreme example.