Ferns, unlike flowering plants, do not produce pollen. Instead, they rely on spores for reproduction. Spores are microscopic asexual reproductive units that develop in structures called sori on the undersides of fern fronds. When mature, the spores are released and dispersed by wind or water to reach new areas for germination. If conditions are favorable, the spores will develop into small gametophyte plants that produce male or female gametes. These gametes unite to form a zygote, which then develops into a new fern sporophyte.