THICK fleshy which grows horizontally into the earth's surface which also has dry scale leaves, terminal bud, and ADVENTITIOUS roots are known as 'Bulb'.The bulbs MAY be fleshy as WELL as tunicated.The stem helps in providing structure and support to the plant. It is modified into three important types:Underground ModificationsSub-aerial ModificationsAerial ModificationsRhizozome is non-green with distinct nodes and internodes.There are auxiliary as well as apical buds.These are brownish in colour.The common types of rhizomes are fleshy due to the storage of food material. It also contains terminal buds. E.g., ginger.Many fleshy scale leaves are present.The base of the bulb consists of a cluster of adventitious roots. E.g., onion, garlic.The bulb may be tunicated or scaley.A sheath of dry MEMBRANOUS scale leaves covers the tunicated bulb.A scaley bulb contains no tunic.The tuber is a fleshy part of the plant which stores food.Potato is the most common tuber largely used as food.The lower part of the potato gets covered by the earth where the adventitious branches grow.It is covered with a number of depressions called “eye” and each eye represents a node.It does not contain adventitious roots.These are largely used as food and grow very slowly.