Abstract: Cellularization of endosperm in peanut was observed with transmission electron microscopy. The free nuclei of endosperm at heart-shaped embryo stage are irregular in shape. Abundant mitochondria, plastids, Golgi bodies, vesicles and some endoplasmic reticulum are present in the cytoplasm of the free nuclear endosperm. The endosperm nodules are usually found at globular and heart-shaped embryo stage. There exist wall ingrowths on the embryo sac wall. Three patterns of endosperm cellularization were observed in different ovules: (1) The initial anticlinal walls arise from the embryo sac wall and grow predominantly by the coalescence of Golgi vesicles and endoplasmic reticulum cisternae. These freely growing walls which have middle lamellae branch and eventually meet to form the endosperm cells. (2) After the mitosis of the nuclei, the cell plates are formed between the sister nuclei. These cell plates grow continuously and branch. The cell plates are observed between the nonsister nuclei too.

Key words: Arachis hypogeae