The correct answer is option 1: Dermatogen.

The histogen is the tissue from which the epidermis is formed during plant development. The epidermis is the outermost layer of cells in plants, and it serves as a protective barrier against environmental stresses. The dermatogen is one of the three primary meristems in plants, along with the periblem and the plerome. The dermatogen gives rise to the dermal tissues, including the epidermis, as well as the associated structures like the root cap and the hairs. The periblem, on the other hand, gives rise to the cortex of the plant, and the plerome gives rise to the vascular tissues. Therefore, option 1, Dermatogen, is the correct answer.