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Typical anatomical cross sections of annual rings in trees. Gymnosperms show mainly longitudinal tracheids that perform both mechanical and hydraulical functions (A). Angiosperms show heterogeneous (B) or homogeneous (C) structures that include large vessels that fulfill only the water conduction function, while mechanical support of the tree is provided by fibers. (A) Larix decidua, (B) Quercus robur, and (C) Fagus sylvatica. Scale bar represents 200 μm.
