Wood anatomy of Elaeagnaceae, with comments on vestured pits, helical thickenings and systematic relationships

The secondary xylem of Elaeagnus, Hippophae. and Shepherdia is described an d illustrated in detail. Shrubs and small trees of Elaeaguaceae have ring-p orous or semi-ring-porous wood with simple perforation plates, vascular tra cheids, fiber-tracheids, diffuse or rarely paratracheal axial parenchyma, a nd uni- or biseriate rays in Hippophae and Shepherdia, but wider rays in El aeagnus. Walls of vessel elements, especially narrow ones, tracheids, or fi ber-tracheids sometimes show helical thickenings; in a few instances these intergrade with small bud-like protrusions associated with pits. Scanning e lectron microscopy illustrates that small to vestigial vestures are present in all species studied, although nonvestured pits are also common. The ana logous nature of vestures and helical thickenings is considered. Comparativ e wood anatomy suggests a rather isolated position of the family Elaeagnace ae; affinities with Rhamnaceae, Proteaceae, and Thymelaeaceae are discussed .