The primary endosperm nucleus in Alyssum maritimum is surrounded by a large number of polysaccharide grains. The grains are utilized during the nuclear development of the endosperm. The nuclear endosperm stains intensely for proteins, DNA and RNA but the concentration of these metabolites declines during cellularization, whereas the polysaccharide content increases again. The cellular endosperm in mature seeds stores polysaccharides mainly in the form of cell walls, and proteins as proteinaceous masses. The endosperm is rich in ribosomes, mitochondria and plastids. The nuclei show different morphology. Nucleoli are either vacuolated or compact. In the endosperm extrusion of spherical bodies from the nuclei occurs.