Almost twenty years ago DE DuvE discovered the existence in rat liver cells of a novel class of subcellular structures which he termed lysosomes. As the lysosomes are the seat of various hydrolytic enzymes this discovery greatly stimulated the interest in cellular digestive processes. It is now recognized that compartmentation of hydrolases is an outstanding example of the dependence of metabolic functions on cell structure. The important role of lytic processes in plant metabolism made it interesting to correlate the facts on the various phenomena and present them from the point of view of...