\Pro*em"bry*o\, n. [Pref. pro- + embryo. ] (Bot.)
(a) The series of cells formed in the ovule of a flowering
    plant after fertilization, but before the formation of
    the embryo.
(b) The primary growth from the spore in certain cryptogamous
    plants; as, the proembryo, or protonema, of mosses.