Slide 12: is a cross section of a monocot root. The bright red cells in a circle make up the endodermis, a tissue which in roots separates the cortex from the vascular tissues. Inside the endodermis, the xylem and phloem are next to each other. The very large cells are the xylem and the smaller green cells are phloem. Monocot roots have a pith composed of parenchyma tissue in the center of the root, inside the vascular ring, in addition to the parenchyma tissue in the cortex. Pith and cortex are very similar, both structurally and functionally, being distinguished from each other primarily by their location relative to the vascular tissue. What is the primary function of the parenchyma cells of the root?