● The `color{violet}("vertical section")` of a `color{violet}("dorsiventral leaf")` through the `color{violet}("lamina")` shows three main parts, namely, `color{violet}"epidermis, mesophyll"` and `color{violet}("vascular system.")`

● The `color{brown}("epidermis")` which covers both the upper surface ( `color{brown}("adaxial epidermis")`) and lower surface ( `color{brown}("abaxial epidermis")`) of the `color{violet}("leaf")` has a conspicuous cuticle.

● The `color{violet}("abaxial epidermis")` generally bears more `color{violet}("stomata ")` than the `color{violet}("adaxial epidermis.")`

● The latter may even `color{violet}("lack stomata.")`

● The `color{violet}("tissue")` between the upper and the lower `color{violet}("epidermis")` is called the `color{brown}("mesophyll.")`

● `color{violet}("Mesophyll,")` which possesses `color{violet}("chloroplasts")` and carry out `color{violet}("photosynthesis,")` is made up of `color{violet}("parenchyma.")`

● It has two types of cells – the `color{brown}("palisade parenchyma")` and the `color{brown}("spongy parenchyma.")`

● The `color{violet}("adaxially")` placed `color{violet}("palisade parenchyma")` is made up of `color{violet}("elongated cells,")` which are arranged vertically and parallel to each other.

● The oval or round and loosely arranged `color{violet}("spongy parenchyma")` is situated below the `color{violet}("palisade cells")` and extends to the lower `color{violet}("epidermis.")`

● There are numerous large spaces and air cavities between these `color{violet}(" cells.")`

● `color{brown}("Vascular system")` includes `color{violet}("vascular bundles,")` which can be seen in the veins and the midrib.

● The size of the `color{violet}("vascular bundles")` are dependent on the size of the veins.

● The veins vary in thickness in the `color{violet}("reticulate venation")` of the `color{violet}("dicot leaves.")`

● The `color{violet}("vascular bundles")` are surrounded by a layer of `color{brown}("thick walled bundle sheath cells.")`

● The `color{violet}("anatomy of isobilateral leaf")` is similar to that of the `color{violet}("dorsiventral leaf")` in many ways.

● It shows the following characteristic differences.

● In an `color{violet}("isobilateral leaf,")` the `color{violet}("stomata")` are present on both the surfaces of the `color{violet}("epidermis;")` and the `color{violet}("mesophyll")` is not differentiated into `color{violet}("palisade")` and `color{violet}("spongy parenchyma.")`

● In `color{violet}("grasses, acertain adaxial epidermal cells")` along the veins modify themselves into large, empty, colourless cells.

● These are called `color{brown}("bulliform cells.")`

● When the `color{violet}("bulliform cells")` in the leaves have absorbed water and are `color{violet}("turgid, the leaf ") ` surface is exposed.

● When they are `color{violet}("flaccid due to water stress,")` they make the leaves curl inwards to minimise water loss.

● The parallel venation in `color{violet}("monocot leaves")` is reflected in the near similar sizes of `color{violet}("vascular bundles")` (except in main veins) as seen in vertical sections of the `color{violet}("leaves.")`