DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Yew tree leaf. Light micrograph of a transverse section through the leaf (pinna) of a yew tree, (Taxus baccata). The structure has xerophytic (drought plants) characteristics. The lower and upper epidermal cells are covered in a thick waterproof cuticle layer. Under the upper epidermis are two layers of palisade mesophyll, below which are the irregular cells of the spongy mesophyll. The vascular bundle (centre) consists of upper xylem tracheid cells (red) and lower phloem sieve cells (blue). A cambium layer is in-between the xylem and phloem. Magnification: x106 when printed 10 centimetres wide.
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