Abstract: The pedicel of E. ferox possesses closed, scattered vascular bundles and contains no cambium. Four main air canals are well developed. Mesophyll of sepal is differentiated into palisade and spongy parenchyma. Petal is simpler in structure than that of sepal with no palisade tissue differentiated. Stamens show a wide varity of shapes; those in the outer whorls are usually petaloid while the inner whorls are of the conventional type bearing four-loculate anthers. Ovary is inferior, multicarpellarv and syncarpous with laminar plancentae in each locule. The flower primordium grows out from the mixed bud. It is enveloped by an axillary scale. The preliminary indication of floral initiation is the periclinal divisions of the second layer of the shoot apex which is closer to the leaf base. By the time a flower primordium becomes 465μm high, the floral parts begin to arise in a continuous acropetal sequences, namely sepals, petals, stamens and carpels successively with initiation of their primordia by periclinal divisions of the second or third layer on the flank of the floral apex respectively. By the fact that the growth of the outer layered cells of the receptacle is faster than those of the inner ones, an epigynous flower and an inferior ovary is thus to be formed. The ventral margin of the carpel has become conduplicately appressed and fused in the lower portion, while the upper part has not been fused, an ovarian canal is appeared from top of the ovary. There is no differentiation of a style. A central receptacular core is found among the carpels. On the basis of anatomical and developmental studies of the floral organs, we suggest that Euryale ferox exhibits a number of most primitive features, such as petaloid stamens, carpel with ovarian canal, elongated receptacle, prominent residual floral apex and laminar placentation. The development of floral parts and characteristics of ovary indicate that genus Euryale is much more similar to Victoria, Nymphae and Nuphar than to Nelumbo and Brasenia.

Key words: Euryale ferox, Floral parts, Structure, Development