Stems are created as an embryo emerges and the shoot apical meristem becomes active and gives rise to the leafy superstructure above the soil. The stems are present in most plants to (in general) support the leaves and reproductive organs and to hold the vascular tissues which move water, ions and products of photosynthesis to their respective destinations. Cotton is an excellent example of a dicot which has both primary and secondary growth in the stems. The stem cross-sections show the eustele organization of the vascular bundles in primary growth and the continuous layers present in secondary growth. The stems also show a clear epidermis, cortex, and pith as well as the above mentioned primary and secondary growth of the vascular bundles. Although we do not have clear pictures of the formation of a phellogen, indeed cotton stems do initiate secondary growth resulting in a periderm with the formation of bark.

Below are links to three pages which illustrate many key aspects of growth and development in the cotton stem.