Abstract:The ultracytochemical localization of ATPase activity was carried out by the method of lead precipitation in the ovules of Antirrhinum majus L. No ATPase activity is observed in the egg apparatus, but some in the polar nuclei, cytoplasm and plasma membrane of the central cell. Between the embryo sac wall and the cuticle surrounding it, there is a gap where some filamentand vesicle-like structures were demonstrated by conventional staining method, and much of ATPase activity is found there. At the chalaza of the ovule, a lot of ATPase particles are found irt the nuclei, plasma membranes and the thick and loose wall of the hypostase cells. The particles of ATPase in the hypostase and those in the gap surrounding embryo sac are continuously distributed through the intervals of the cuticle at the chalazal end of the embryo sac. Some of ATPase particles are found on the plasma membranes and plasmadesmata of integument ceils, noticeably much more in the nucleoplasm of the integumentary tapetum. According to the ATPase distribution pattern in the ovules, we suggest that the function of the integumentary tapetum and hypostase is secretion, and that the gap surrounding the embryo sac may be an apoplastic ehannal for nutrient flow into the embryo sac.