Green spores of Equisetum diffusum D. Don (Equisetaceae). The spores have four strap-like appendages, called elaters, that coil and uncoil in response to changes in humidity. When the air is dry they extend outward and create wind resistance for spore dispersal. When the air gets humid, the elaters coil around the spore so that buoyancy decreases and the spore drops onto moist soil.
