Acrogen \Ac"ro*gen\, n. [Gr. 'a`kros extreme, high + -gen.] (Bot.) A plant of the highest class of cryptogams, including the ferns, etc. See {Cryptogamia}. [1913 Webster] {The Age of Acrogens} (Geol.), the age of coal plants, or the carboniferous era. [1913 Webster]