histogen theory

A concept of the organization and development of the apical meristem, in which the meristematic region is differentiated into three main zones, the dermatogen, periblem, and plerome. The dermatogen is supposed to give rise to the epidermis, the periblem to the cortex, and the plerome to all the primary tissues internal to the cortex. This theory has largely been replaced by the *tunicacorpus theory.