Fig. 16.2-5. Transverse section of a cactus. This cactus is a bit unusual: it has wide rays (the two parenchymatous regions on either side of the micrograph), a narrow mass of parenchymatous axial wood with a few vessels and many axial parenchyma cells, and just a small amount of active phloem. As sieve tube members and companion cells collapse, surrounding ray parenchyma cells swell and crush the phloem into a narrow radial band rather than the more typical flat tangential bands as in Fig. 16.2-4.