DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Oleander stem. Light micrograph of a cross-section through the stem of an oleander (Nerium oleander) tree. The outer layer is a thick cuticle (yellow) and then cork cambium (blue-green). The upper cortex is made of collenchyma and the lower cortex has a ring of bundles of phloem fibres (deep blue) underneath which is a ring of phloem with sieve tubes (green). Under this is a thin ring of xylem (black and red) with vascular bundles at the corners. The pith (centre) is made up of large parenchyma cells. Magnification: x14 when printed 10 centimetres wide.
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