The results indicate that leaves of C. pseudocuraica from five different environments exist the same structure.They are all made up of epidermis, mesophyll and nervure.
Ground meristem The central region of the apical meristem from which the ground tissues of pith, cortex, medullary rays, and mesophyll differentiate. In root meristem it is also called periblem.
So the carbon dioxide comes in through the stomata, makes it's way through gaps in the airy layer of cells (called spongy mesophyll) at the bottom part of the leaf, then heads up to the palisade layer for photosynthesis.