During the period of maturation after imbibition by the seed, but before the administration of the dormancy-breaking stimulus, changes observed in the radicle meristem cells included the disappearance of lipid bodies accompanied by a decrease in extractable lipid from 20% to 4% of the dry weight of the embryo, an increase of protein from 14% to 24% and the appearance of starch. The development of plastids into amyloplasts, during which they became associated with the ER, is described. Originally, a tubular network of rough ER was present but an additional, localized system of parallel arrays of sheet-like rough ER appeared in each cell. A system of multivesicular and other paramural bodies developed, together with microbodies possessing crystalline cores. Golgi bodies, originally rare, became very numerous and appeared to be connected with the tubular ER system. Thus, food interconversions, wall development and the appearance and proliferation of cellular organelles all occurred during deep embryo dormancy, when actual germination was not possible.