The form of the tuber is of taxonomic importance; There are two main types. A verticulate tuber is discoid or depressed-globose, with the shoot apearing from nera the centre of the upper surface. A horizontal tuber is irregularly cylindrical, with the axis of the cylinder horizontal and the shoot appearing at one end of the axis. Young tubers are often abberant in form; The character should be judged by inspection od several mature tubers.
Species and images: