Fig.
8.3-3. Transverse section of old stem of grape (Vitis).
Fig. 8.1-5 showed secondary phloem of grape while the phloem was still young and
functional. The sample shown here was taken from a stem that was much older; the
sieve tube members and companion cells have collapsed into the solid, dark red
mass shown here. The fibers cannot collapse, of course, due to their
thick, lignified walls, so they are still visible here, but all the other cells
are virtually unrecognizable.