Horsetail (Equisetum palustre) stem. Light micrograph of a section through a young stem from a marsh horsetail plant, showing the developing branches (dark green) and leaves (blue). The lignified epidermis has stomata (pores). The cortex consists of outer sclerenchyma cells and inner parenchyma cells (green) and a ring of vallecular canals. The vallecular canals are the vascular bundles, (dark green) and are surrounded by the endodermis and pericycle. Each vascular bundle consists of metaxylem, protoxylem and phloem sieve tube cells. At centre is the pith. Magnification: x3 when printed 10 centimetres wide