Now return to your examination of the leaf cross section at the microscope. The veins pass through and across the section of leaf tissue on your slide. The veins consist of two bundles of elongated cells, each bundle like a handful of straws. The cells are bundled side to side, but are connected end to end along the length of the vein. This tissue consists mostly of dead, elongated cells, attached end to end, with the endwalls missing or perforated.
Lignin picks up the red dye so the walls appear pinkish.
Water and minerals from the soil come into the leaf through these xylem cells. The water is brought there mostly by evaporative forces generated by gas exchange at the epidermis. The bundle of cells closer to the lower epidermis is the phloem tissue. This tissue consists mostly of living, elongated cells, attached end to end, with perforated endwalls. The sidewalls of phloem cells are relatively thin and pick up only the green dye.