Abstract: During the development of cotyledons,the vacuome in mesophyllous cells undergoes dras- tic changes both in morphology and structure.In developmental stage I,vacuome appears in the meristematic type with several small single vacuoles.1-2 days later,as soon as the central vacuole started to form,the whole vacuome started to transform into differentiated type.Then many new small vacuoles appeared in cytoplasm and bigger vacuoles.The sources and the de- veloping patterns of vacuoles of N.nucifera are diverse and tonoplasts may be formed through: (1)vacuolization and release of the swollen part of the outlayer of nuclear membrane;(2)re- lease and enlargement of the swollen end of dictyosome;(3) budding of tube-like endoplasmic reticulum or release of its swollen end,loss of ribosomes and deformation;(4) invagination of plasmalemma and pinocytosis of a small part of cytoplasm or a drop of vegetative liquid; and (5) division of the center vacuole with boundles of cytoplasm into several-small parts. During developmetal stage Ⅱ and Ⅲ,the bigger vacuoles divided into smaller ones and the smaller vacuoles fused with each other again.Finally,many vacuole groups with diameters averaging 0.4-1.2 milli micron were formed.They developed in various patterns into lyso- somes,spherosomes,microsomes,paramural bodies,autophagic vacuoles,pinocytic vesicles and so on.Some vacuoles later developed into protein bodies and lipid bodies.The article proved that the structure and function of vacuome in cytoledon cells of lotus are similar to those in cytoledon cells of other dicotyledons.