Fig. 8.2-3. Longitudinal section of sieve tube member in milkweed. In this section, the two sieve plates are oriented such that we see the right one in face view, the left one at an angle, but not directly from the side as in Fig. 8.2-2. They almost appear to be blockages in single long cells, but remember that sieve plates are where two sieve tube members contact each other. Like perforation plates, each sieve plate actually consists of the plate of one sieve tube member contacting the sieve plate of another, with their sieve pores aligned.