There are two distinct types of roots formed in some bulbs and corms. There is the fibrous root system that develops adventitiously at the base of the bulb or corm.
These roots function in water and nutrient uptake. The second root form consists of contractile roots that function to adjust the depth of the bulb or corm in the soil.
These thickened roots expand and contract to pull the bulb or corm down to its proper soil depth.