The flight of the dandelion

Dandelion seeds float through the air suspended by a structure called the pappus—a ring of bristles that looks rather like the brush of a chimney sweep, only in miniature. But wouldn't a solid parachute-like structure be better? Naomi Nakayama and colleagues show that by virtue of its porosity, the pappus entrains a toroidal vortex of air rather like a smoke ring, and this keeps it aloft, rather as if it generates its own hot-air balloon. This may be an entirely new mechanism to add to the many ingenious schemes living things use to stay suspended in mid-air.