Fig. 8.2-8. High magnification of cucumber phloem. This micrograph has a prominent sieve plate and P-protein plug, but also shows that sieve tube members can have multiple companion cells. Each pair of arrows indicates the two companion cells for one sieve tube member (the lower pair of arrows lies in the sieve tube member; the two upper companion cells are associated with the cell just above them and almost out of view). In this species we see companion cells side by side, but in other species, a sieve tube member might be accompanied by a row of companion cells in a linear arrangement down one side.