DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Dog rose stem. Polarised light micrograph of a cross-section through the stem of a dog rose (Rosa canina) plant. The outer cortex (black and red) is made of cork cambium tissue, beneath which is a ring of phloem and sieve tube bundles (yellow). Under this is a ring of cambium (dark blue) and then woody fibres (green). The solid pith (centre, blue) is composed of large parenchyma cells. Magnification: x14 when printed 10 centimetres wide.
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