(Recorded at 10,000 fps with a 0.097 ms exposure displayed at 15 fps.) A clear 'mushroom cloud' vortex ring forms and reaches a nearly fixed width within 0.5 ms. Explosion of a Sphagnum palustre capsule. Dolphins produce water vortex rings jellyfish and squid use water rings to push themselves along, the human heart pushes blood from one chamber to another using vortex rings, and of course humans who smoke can produce smoke rings. Several animals are known to make vortex rings, but until now no plant has been known to do so. The leading edge pushes against the atmosphere but then rolls back to form a donut-shaped ring. The vortex ring is produced as the air trapped in the capsule explodes outwards.

The process takes under one hundredth of a millisecond. When the air pressure reaches a critical point the capsule blows its top off, shooting spores and air upwards to reach the turbulent layer at about 10 cm high. As it dries out the capsule collapses in on itself to form a cylinder, with the air compressed inside it. The tip of each stalk contains from 20-250,000 spores in a spherical, waterlogged capsule that dehydrates on sunny days. The vortex overtakes and moves past the cap. The spores in the wake move upwards at a slower rate than those in the bubble. (Recorded at 10,000 fps with a 0.020 ms exposure displayed at 15 fps.) The vortex bubble and trailing wake are visible. Their films revealed that a tiny “mushroom cloud” or vortex ring accompanies each firing, and it is the vortex rings that give the spores the extra boost required to reach a good height to catch the wind.

Physicist Dwight Whitaker from Pomona College, California and botanist Joan Edwards from Williams College, Massachusetts, solved the mystery by filming the mosses firing spores from the stalks, using ultra-high speed cameras shooting up to 100,000 frames a second.

Spore mushroom