Root contraction is effected in many species by redirected growth of parenchyma cells, supplemented in some cases by other processes. In Hyacinthus, root contraction is associated with the growth of inner cortical cells, which after becoming fully elongated in the normal growth of the root, then expand radially and contract longitudinally. The contraction is, however, a growth process, since it occurs in turgid tissue and is partly reversible by plasmolysis. Moreover, the radial walls of the cells concerned increase in area and the cells increase in volume. The changes in cell shape associated with contraction involve changes in cell-wall structure which, in so far as they are detectable by polarization microscopy, are described and discussed in the light of current views on cell-wall growth.