Image: primary stem of a dicot, a buttercup, stained with safranin / Alcian blue.
Epidermis: it is the outermost layer of the stem. In this case, the epidermal cells do not show a thick cuticle, although their free surface is irregular.
Cortical parenchyma: it is a layer of parenchyma cells found between the epidermis and vascular bundles. Parenchyma cells are large cells with thin cell walls colored in blue.
Sclerenchyma fibers: these cells are organized around the vascular bundles as a cylinder, providing mechanical support. They exhibit lignified cell walls stained in red.
Primary phloem: it is the vascular tissue specialized in transporting organic molecules. The primary phloem cells are small, with thin cell wall stained in blue, and form a small group in each vascular bundle.
Procambium: it is the meristem found in the vascular bundles. The procambium is located between the primary phloem and the primary xylem. The procambium cells proliferate and differentiate phloema outward and xylem inward.
Primary xylem: it is the vascular tissue specialized in transporting water and minerals. The primary xylema consists of large conducting cells (cell walls stained in red), small supporting sclerenchyma fibers (cell walls in red), and small parenchyma cells (cell walls in blue).
Pith: the central part of the stem, below the vascular bundles, is made up of parenchyma cells. They are large cells with cell walls stained in blue.