Phytolacca is the most original and biggest genus in Phytolaccaceae and one special genus in plant systematic studies as well. The light microscopy observation results show that Ph. americana L. ovule arises from caulis (floral receptacle). The perisperm and hypostase are initiated from the top several layers cells of chalaza simultaneously after fertilizing, and the perisperm is located between nucellus and hypostase. The hypostase cells are thin-walled with dense cytoplasm, clear nuclear, and some reserve granules in earlier stage, and change to thick-walled and dead cells at heart-shaped embryo stage. Its main function may maintain the cellular division and perisperm growth without delivering nutrient materials to perisperm. Furthermore, an evolutionary picture of placentation in Caryophyllales is presented by authors