The development of the endosperm inAllium cepaconforms to the free-nuclear type. The cytoplasm of the endosperm at the caecal region is denser, rich in RNA and proteins but low in diffused polysaccharides. There are more triploid nuclei per unit area in this region than elsewhere. The small cells of the hypostase are rich in RNA and proteins. This may well result from the high rate of perfusion of nutrients through the hypostase at this time.