Bulb: An underground storage organ, consisting of leaves modified for storage (called scales), which can be solitary or many and which are most commonly fleshy and attached to a basal plate of solid tissue, enclosing the growing point.
Bulbil: Small bulbs growing on the stem either underground or in the axils of the leaves, or in certain species in the florescence.
Bulblet: Small bulbs produced around the parent bulb.
Corm: An underground storage organ of solid material, being a swollen part of a stem, and not having scales as a true bulb. Often refered to as bulb as in crocus bulb or gladiolus bulb.
Rhizome: A thick horizontal underground stem from which buds and roots develop. Usually persistent from year to year.
Tuber: A short and thick swollen, generally underground organ, often but not always capable of producing shoots.
Tuberous Root: Tuberous roots look like tubers, but are actually swollen, nutrient-storing root tissue. During the growing season, they put out fibrous roots to take up moisture and nutrients. New growth buds, or eyes, form at the base of the stem where it meets the tuberous root. This area is called the crown.