der·mat·o·gen \(ˌ)dərˈmad.əjə̇n, -ˌjen, ˈdərməd.ə-\noun (-s) Etymology: International Scientific Vocabulary dermat- + -gen 1.: the outer primary meristem of a plant or plant part that according to the histogen theory gives rise to epidermis 2.: the outer apical meristem of a root tip — called also protoderm