Bulb is a term given to plants that have fleshy underground storage structures, but only some of the plants commonly called bulbs are actually true bulbs. Tubers are also bulbs by this definition, but they are not true bulbs. A true bulb and a tuber are different in appearance and in how they grow. However, they serve the same function, which is to store food and energy that helps plants survive during the winter or dry months. True Bulb IdentificationBulbs are typically round to oval in shape, with a pointed top. If you cut a true bulb in half vertically, you can see the parts inside. The bottom or basal portion of the bulb typically cradles a tiny bud, which in some plants, already resembles a flower. Surrounding the bud are white, fleshy scales that contain all the food the bulb needs. The basal plate, at the bottom of the bulb, anchors the scales and the floral stock to the bulb and holds the plant’s roots. Many true bulbs are protected by a tunic, a thin outer skin. Onions, tulips, narcissus and lilies are examples of true bulbs. While tubers are a food and energy storage structure like true bulbs, they are very different in appearance. Tubers are basically enlarged stem tissue and do not have a basal plate or papery tunic. They also come in a variety of shapes and may be flat or cylindrical. Tubers may also come in clusters. Potatoes, begonias and dahlias are examples of tubers. Reproduction and GrowthNew bulbs often form around the original bulb. These are called offsets and develop from buds within the base of the original bulb to produce new plants. Tubers do not grow from a single point. Instead, the buds -- sometimes referred to as eyes -- develop over the surface of the tuber, so stems can appear from the sides as well as the ends. New plants can be grown from tuber cuttings containing buds or eyes, or from seeds. True bulbs are either tunicate or non-tunicate. Tunicate bulbs have a papery tunic that protects the scales from injury and drying. Tulips, hyacinths, daffodils and alliums are tunicate bulbs. A non-tunicate bulb does not have a tunic to protect the scales, so these bulbs must be kept consistently moist before planting. A lily is an example of a non-tunicate bulb. Tubers also come in two types: stem or tuberous root. Stem tubers are formed from thickened stolons or rhizomes. Shoots are produced on the top sides of the tuber that later grow into stems and leaves. The undersides of stem tubers produce roots. Tuberous roots are also referred to as storage roots and are a lateral root that enlarges to function as a storage organ. The enlarged area of this type of tuber may form at the end of the root or the middle, or it may encompass the entire root. Potatoes are root tubers, while begonias are stem tubers.- Jupiterimages/Creatas/Getty Images