Fig.
8.1-7b. High magnification view of phloem in roots of catclaw. The
large phloem cells are the sieve tube members, and the very small ones
(indicated by two arrows) are companion cells. Even though this is a very high
magnification view, the cells are so small that almost no detail is visible. The
entire mass of phloem -- more than 20 cells -- could fit inside one of the
medium-size vessel elements.