Fig.
11.5-7. Transverse section of cosmos
stem (Cosmos). This micrograph emphasizes the protoxylem portion of the
primary xylem. Three rows of vessels are visible, and the arrows indicate two
protoxylem vessels that have been torn apart, their secondary walls broken. It
is important to emphasize here that the xylem is a complex tissue, containing
not just the vessel elements, but also the parenchyma between them.