DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Horse-tail stem. Light micrograph of a section through the stem of an Equisetum sp. horse-tail plant. Outside the stem are whorls of leaves (red and blue) containing chloroplasts. The stem has an outer epidermis and outer cortex, which is lignified and silicified. The vascular bundles (small circles) consist of the xylem (outer side) and poorly developed phloem (inner side). The central pith has broken down leaving a hollow (central white area). Magnification: x5 when printed 10 centimetres wide.
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