Encyclopædia Britannica, Ninth Edition/Acrogenæ

ACROGENÆ is the name applied to a division of acoty ledonous or cryptogamous plants, in which leaves are pre sent along with vascular tissue. In the higher divisions of Acrogens,as ferns and lycopods, the tissue consists of scalari- form vessels, while in the lower divisions spiral cells are observed, which take the place of vessels. The term Aero- gen means summit-grower, that is, a plant in which the stem increases specially by the summit. This is not, however, strictly accurate.