DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Squash stem. Light micrograph of a transverse section through the stem of a squash (Cucurbita sp.) plant. The stem ground tissue is parenchyma (light blue) with a ring of ten bicollateral vascular bundles (five outer and four inner rings). These bundles are made up of central xylem tissue (red) with large vessels. At the top and bottom of the xylem are oval-shaped areas of phloem, made up of large sieve tubes with perforated sieve plates (cobalt-blue). Magnification: x37 when printed 10 centimetres wide.
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