Dryas octopetala
The Younger Dryas, Older Dryas and Oldest Dryas stadials are named after "Dryas octopetala", because of the great quantities of its pollen found in cores dating from those times. During these cold spells, "Dryas octopetala" was much more widely distributed than it is today, as large parts of the northern hemisphere that are now covered by forests were replaced in the cold periods by tundra.