All other cells are tracheary elements in various developmental stages. Side wall between two differentiating vessel members. Large arrows indicate the probable limits of the middle lamella, triangles, connections between the microtubules and plasmalemma. Side wall between two differentiating vessel members. The protoplast is somewhat denser in the younger cell.
Stars indicate membrane-bound compartments one of which appears as a bleb from the plasmalemma.
Side wall between two vessel members with differentiating helical thickenings that appear in sections. The cell to the right is more advanced in development than the one to the left as is indicated by larger amount of secondary wall deposition. Open arrows point to vesicles between plasmalemma and secondary wall. In the older cell, the secondary wall is marked swl, in the younger sw22. Stars indicate membrane-bound vesicles one of which appears as a bleb from the plasmalemma.