Fig.
11.3-3. Transverse section of sweetflag (Acorus). Sweetflag
grows in wet, marshy areas, and its
cortex develops as a thick region of aerenchyma – all the white
areas here are intercellular spaces and both oxygen and carbon dioxide can
diffuse rapidly through the stem tissues. Notice that the outermost layers of
cortex are compact -- the intercellular spaces there are so small that we cannot
see them at this magnification. Because the outer layers of the cortex are
different from the rest of the cortex, the region could be considered to be a
hypodermis. The epidermis consists of parenchyma cells with very thin walls; its
cuticle is just thick enough that we can see a hint of pink at this low
magnification.