Some observations on the course of the vessels in the wood of Fraxinus excelsior L.

The vessels in the secondary xylem of Fraxinus excelsior, while running through the wood in a longitudinal direction, show a tangentially and radially curved course. Vessels are in contact over widely differing distances. The result is a rather loose three-dimensional vascular network. The phenomena are discussed from an ontogenetical point of view, in relation to prevailing concepts of cambial activity.