Radial view of locust cambium & derivatives

In this radial view (along a vertical axis) of black locust (Robinia pseudo-acacia) stem is shown the very narrow, elongate shape of the fusiform cells of the vascular cambium.

On the right note a mature sieve tube with callose deposits (seen as blue-colored plates due to the resorcin blue stain employed) over a sieve plate in secondary phloem, and on the left tracheary elements with helical thickenings of lateral walls in secondary xylem (wood) may be observed.