Differentiating meristem region of a broccoli flower bud (Brassica oleracea italica), animated coloured scanning electron micrograph (SEM). Shown here is a differentiating meristem cell. The meristem cell is differentiating in to an epidermal cell that contains a stoma with guard cells. Apical meristems are the completely undifferentiated (indeterminate) meristems in a plant however close by the differentiation of specialized cells takes place. Broccoli is one of several vegetables in the species Brassica oleracea, in the family Brassicaceae (Cabbage Family). Broccoli possesses numerous fleshy flower heads (usually green in colour) arranged in a tree-like fashion on branches growing from a thick stalk.