Radicles and adventitious roots of the soap plant are contractile and through their activity, mature bulbs of this species are buried to depths of 20–30 cm. Experiments were performed to determine rates of contraction and displacement of the shoot apex resulting from activity of the contractile radicle and the first several adventitious roots. The average displacement was 23.2 mm over a 10‐wk period and 63.8 mm over 29 weeks. Small glass beads and abortive seeds served as controls and showed no displacement through the soil column. Measurements from longitudinal and transverse sections of contracted and uncontracted portions of radicles revealed average increases of 26–64% in radial dimensions and 40–56% decreases in longitudinal dimensions of inner and middle cortical cells (excluding the endodermis) following contraction. Cells of the outermost cortex (excluding the exodermis) decreased in average longitudinal dimensions by 18–26% before becoming distorted and collapsed as contraction was completed. Average volumes of innermost cortical cells decreased by 15–54%, while two or three cell layers of the middle cortex, adjacent to collapsed outer cortical cells, increased in volume up to 75%. These middle cortical cells are identified as the “active” cells which, by their growth, are responsible for the shortening of the root. Throughout the process of contraction, the stele remains straight and undistorted, although the closer spacing of tracheary element secondary wall thickenings following contraction suggests longitudinal compression of the stele. The average number of cortical cells per transverse section does not differ in contracted and uncontracted roots and no evidence is found to support the “interdigitation” hypothesis of root contraction. However, reorientation of middle cortical cell expansion may be the mechanism of root contraction inChlorogalum pomeridianum.