Ex'o-gen, n.

n. [Fr. exogène, from Gr. ἔξω, outside, from ἐξ, out, and γενεῖν, γενέσθαι, to bring forth, to be born.] (Bot.) A plant belonging to one of the great primary classes which includes the greater part of the vegetable kingdom, and in which the plants are characterized by having distinct wood, bark, and pith, the wood forming a layer between the other two, and increasing by the annual addition of a new layer to the outside next to the bark. The leaves are netted-veined, and the number of cotyledons is two, or very rarely several in a whorl. Gray.