DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Scanning electron micrograph of the wood (secondary xylem) of the Scots pine, Pinus sylvestris showing both vertical (bottom) & horizontal (top) cut surfaces. The large-celled wood at right is early (spring) growth; the late wood (left) has small, thick- walled cells and is much denser. The vertical tube- like structures seen in both early and late wood are tracheids. In softwoods like pine, these carry out both sap- conducting and mechanical functions; the large early tracheids are primarily concerned with conduction, whereas the much smaller late ones act primarily as structural elements. Magnification: x60 at 8x10 inch size.
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