Proembryo \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.
[1913 Webster]