Image: primary stem of a dicot, stained with safranin / Alcian blue.
Epidermis: it is the outer layer of the stem. In this case, the epidermis consists of cells without a well-developed cuticle.
Sclerenchyma: sclerenchyma fibers are found covering the primary phloem, organized in bundles, forming the so-called bundle cap.
Primary phloem: it is the vascular tissue specialized in transporting organic molecules. Primary phloem is composed of a small group of cells in each vascular bundle, showing thin cell walls.
Procambium: it is the meristem that produces the two primary vascular tissues: phloem toward the outer part and xylem toward the inner part. The procambium is made up of one or two rows of undifferentiated cells.
Primary xylem: it is the vascular tissue specialized in transporting water and minerals. The primary xylem is made up of large cells with lignified cell walls (in red) and small cells with thin blue-green cell walls (parenchyma) and with red cell walls (sclerenchyma).
Parenchyma: this tissue constitutes the major part of the stem, both cortical and pith regions. Parenchyma cells are usually large with thin cell walls colored in green-blue.