This group gathers Ferns and Fern Allies subcategory members belonging to the class Polypodiopsida, the true ferns, by far the largest and most diverse group of ferns, found in nearly every terrestrial habitat on Earth except the driest deserts and permanent ice. It spans familiar temperate woodland species with the broad, finely divided fronds most people picture when they think of a fern, ferns adapted to open, sunny habitats with tougher, more upright fronds, and epiphytic species that grow attached to tree trunks and branches rather than rooted in soil. Nearly every true fern reproduces through microscopic spores released from structures called sori on the underside of the frond rather than through seeds or flowers, and most unfurl new fronds from a tightly coiled shape called a fiddlehead or crozier, a growth pattern found in ferns and their relatives but in essentially no flowering plant.