Thăl'lo-gĕn, n.

n. [Gr. θαλλός, young shoot or branch, frond, and γένεσιν, to beget, generate.] (Bot.) One of a large class of cellular, cryptogamous plants, consisting of parenchyma alone, forming a mass or stratum, or consisting of a congeries of cells, or even of separate cells, and never exhibiting a marked distinction into root, stem, and foliage, or into axis and leaves;—called also thallophyte. In the plants of this class, which includes the lichens, fungi, algæ, and the like, reproduction takes place by spores. Gray. Baird.