Perisperm, the nutritive tissue of the seed which originates from the tercine (q.v.), or nucellus, outside the embryo-sac. It consists mainly of thin-walled parenchymatous cells rich in starch or oil, and, together with the endosperm (q.v.) within the embryo-sac, constitutes what was formerly known as albumen (q.v.). With the exception of some Alismaceas and Orchidaceas, almost all spermaphytes have perisperm in the early stages of the development of the seed; but in "exalbuminous" seeds it, together with the endosperm, is absorbed before the seed is ripe.