Vascular bundles in the stem contain xylem and phloem, which are scattered in monocots and form a ring in dicots. Between a stem's epidermis and vascular tissue lies the cortex, made of ground tissue. Pith is storage ground tissue in the center of a stem. Stem modifications include stolons, thorns, succulent stems, tendrils, and tubers. Leaf organization may be alternate, opposite, or whorled.
Leaves are the sites of photosynthesis.
Leaf epidermis is tightly packed, transparent, and nonphotosynthetic. Veins may be in either netted or parallel formation. Leaf ground tissue includes palisade and spongy mesophyll cells. Leaf modifications include tendrils, spines, bracts, storage leaves, insect-trapping leaves, and cotyledons. Leaves are shed from an abscission zone in response to environmental cues.