Abstract: Ranalisma rostratum is a aquatic and endangered plant.Its seed consisted of no endosperm, and the reserve constituents were stored in the embryo itself by the form of starch grains and protein bodies.Much more starch grains and protein bodies were presented in either the cotyledon or hypocotyl cells, and less in both plumule and radicle meristematic cells.During the stages following germination, the protein bodies were utilized first and they all disapperd as soon as the radicle protruded the seed-coat.The starch grains degraded progressively and complete disorganization taken place at the two-leaf seedling stage.It was presumed that the rapid degradation of protein bodies in the embryo probably caused the high mortality of Ranalisma rostratum seedlings, and this might be one of the reasons which caused the plant into a endangered state.