Cotton leaf. Light micrograph (LM) of a transverse section through the leaf (pinna) of a cotton plant. The cotton plant is a dicotyledonous shrub native to tropical and subtropical regions around the world, including the Americas, Africa, Egypt and India. Present is a central vascular bundle made up of phloem sieve cells (blue) and xylem tracheids (red). Dicot leaves are dorsoventral as the upper and lower surfaces of the leaves are distinguished. The vascular bundle is large in dicot leaf whereas in monocot leaf, both small and large parallel vascular bundles are present. Magnification: x20 when printed at 10 centimetres wide.