Ăc'ro-ġen, n.

n. [Gr. ἄκρος, extreme, highest, and γίγνεσθαι, to be born.] (Bot.) A plant of the highest tribe of Cryptogams, including the ferns, &c. See CRYPTOGAMA.

The age of acrogens (Geol.), the age of coal-plants, or the carboniferous era, when the Sigillaria, Lepidodendra, Calamites, Ferns, &c., were the characteristic vegetation of the globe. Dana.