Slide 28: high power view of a vascular ray. Locate the vascular cambium (green brick wall-like cells running from top to bottom). To the right of the cambium is the secondary xylem. To the left side is the secondary phloem. The vascular ray is funnel-shaped; it is several cell layers thick in the xylem, but expands greatly in the phloem. Some of the rays in secondary phloem will become very wide as the stem increases in girth; this is one way in which the tissues outside the cambium keep up with the increase in girth as new xylem cells are produced. Rays function in lateral transport; nutrients move through plasmodesmata from the secondary phloem through the vascular cambium to the living (parenchyma) cells of the secondary xylem. Although some water flows from the xylem to the phloem through the symplast of vascular rays, much of the water movement is through the apoplast system.