Archegonium is the female organ of spore plants in which eggs are formed. Archegonium is a growth on the surface of the growth of ferns, horsetails, lycophytes and some other spore-bearing plants. Inside the archegonium there is a cavity in which the egg is formed. During fertilization, the contents of the sperm (male reproductive cell) merge with the egg, resulting in the formation of a zygote - the first cell of a new sporophyte. Thus, the archegonium plays an important role in sexual reproduction and the life cycle of spore plants.