"fuckyeahplantae:  Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem  4. Phloem  5. Sclerenchyma  6. Cortex 7. Epidermis Stolen from this Wikipedia article: http://en.wikipedia.org/wiki/Cortex_%28botany%29  after I saw an illustration that said the purpose of the cortex was to ""protect the stem"" and I was like bitches, please. The cortex has soooo many other functions besides bodyguard. Its cells are largely undifferentiated, meaning they can become and later do just about anything. Cortical cells can store carbohydrates, resins, tannins, and tons of other substances. The innermost layer of cortical cells is differentiated into a layer called the endodermis, which helps a plant regulate water and nutrient movement. Some cortical cells even have chloroplasts, and we all know how important photosynthesis is to a plant…"