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.