Potassium antimonite was used to locate calcium in the anthers of lettuce (Lactuca sativa). There are no calcium precipitates in young anthers. After meiosis of microspore mother cells, calcium precipitates first appear in the tapetal cells, from which some small secretive vesicles containing many calcium precipitates are secreted into the locule. At a late stage of the microspore, tapetal cells completely degenerate and their protoplasts move into the locule with many calcium precipitates. The calcium precipitates increase in the early microspores, and in the exine. When the microspores form some small vacuoles containing calcium precipitates, and those vacuoles then fuse to form a large one, the calcium precipitates evidently decrease. The large vacuole of bicellular pollen grain discomposes and calcium precipitates again appear in the cytoplasm and then decrease. When the pollen matures, most calcium precipitates are located in its exine with only a few in the cytoplasm.