Light micrograph of a transverse section through the stem of a marestail plant, showing a single circular group of vascular tissues. The appearance of this stem is typical of that of an aquatic plant, where the amount of vascular tissue is greatly reduced. Here, a simple ring of xylem vessels (small white circles) is surrounded by a more dense band of phloem. The red band of phloem is enclosed by a single layer of pericycle cells and an outer endodermis. The surrounding chain- like tissue is the cortical parenchyma. There is no separation of the vascular tissue into bundles. Magnification: x25 at 6x6cm size.