DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Geranium stem. Light micrograph of a section through a young stem of a geranium (Pelargonium sp.) plant. The outer stem is covered with a thin epidermis (red) which has stomata. Under the epidermis are two layers of flexible collenchyma tissue (dark red) for support. The outer cortex is made of parenchyma tissue (purple with red circles) and an inner ring of sclerenchyma fibres (violet-red). The fibres join the vascular bundles which have an outer phloem (purple), sieve plates and companion cells, with an inner layer of xylem vessels (violet) and parenchyma. Filling the centre of the stem is a pith a parenchyma. Magnification: x13 when printed 10 centimetres wide.
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