The female gametangium of the red algae (see rhodophyta). Carpogonia, which are found at the tips of the female gametophyte, are flask-shaped structures from which protrudes a slender elongation called a trichogyne. The nonmotile male spermatia, released from the antheridia, attach to the trichogyne during sexual reproduction. After fertilization the carpogonium develops into the cystocarp, which contains the carpospores.