Fig.
11.3-7.
Transverse section of cactus stem (Gymnocalycium megatae; no common
name). This cactus
too has cortical bundles that carry sugars away from the outermost,
chlorenchymatous cortex to the phloem of the stele. The cortical bundles also
carry water from the stele xylem outward throughout the cortex, replacing the
water that is lost by transpiration (even though cacti have very
thick cuticles, they still lose water). The size of cortical bundles varies
greatly from species to species; in this species, an entire cortical bundle is
much smaller than ordinary cortex parenchyma cells.