The cortex in plants is primarily composed of parenchyma cells. These are relatively simple, undifferentiated cells with thin cell walls and large vacuoles. They perform a variety of functions, including:

* Storage: Parenchyma cells store water, carbohydrates, proteins, and other nutrients.

* Photosynthesis: In some cases, parenchyma cells in the cortex can contain chloroplasts and contribute to photosynthesis.

* Gas exchange: Parenchyma cells in the cortex can facilitate the exchange of gases between the internal tissues and the environment.

* Support: While not as strong as other cell types like sclerenchyma, parenchyma cells contribute to the overall structure of the cortex.

In addition to parenchyma cells, the cortex may also contain other cell types in smaller amounts, depending on the specific plant species and tissue:

* Collenchyma: These cells have thicker cell walls than parenchyma and provide additional structural support, particularly in young stems and leaves.

* Sclerenchyma: These cells have very thick, lignified cell walls and are responsible for providing rigid support to the plant. They are less common in the cortex but can be found in some cases.

* Secretory cells: These cells produce and store various substances, such as resins, oils, or latex. They are not always present in the cortex but can be found in certain plants.

It's important to note that the composition of the cortex can vary significantly depending on the plant species, tissue, and developmental stage. However, parenchyma cells are the dominant cell type in most cases.