Fig. 6.2-2. Longitudinal section of shoot tip of coleus (Coleus). Two types of meristem are present here, based on the types of tissues they produce. The outermost layer of cells across the top of the apical meristem and leaf primordium is a meristem called the protoderm: its cells are still dividing and their progeny cells will develop into epidermis cells. The two cells bulging from the protoderm of the leaf primordium will develop into trichomes -- they are trichome initials, and they can also be called trichome meristemoids.

            Look carefully at the center of the shoot apical meristem, at the cells just below the protoderm. They are slightly larger, slightly more irregular than the cells on the periphery of the meristem; as these central cells divide and enlarge, they push surrounding cells into the peripheral region. This push causes the cells to move from one part of the meristem to a different part, basically these central cells produce the cells for the rest of the meristem. Such a region is called a promeristem. The promeristem in this species is not particularly easy to see.