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Photographic gallery.  Thousands of particles under the microscope.

Helical Thickening

Helical thickening appears as helical strings wrapping around the cell. The spacing between these strings may be regular or very irregular, depending on the species of wood. In Hardwoods they are most common in the vessel walls. In Softwoods they occur on the tracheids of Douglas fir (Pseudotsuga), Yew (Taxus), and Torreya (Torreya).

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