Abstract: The outer morphology and micromorphology as well as the structure of nectaries of 74 species and 1 variety，belonging to 9 tribes and 36 genera of Cruciferae，were examined by light microscope (LM) and scanning electron microscope (SEM) to reveal the morphological structure and the evolutionary trends of floral nectaries．The floral nectaries of Cruciferae were an outgrowth of receptacle．The anatomical features of floral nectaries showed that the internal structure was comparatively consistent．They were composed of the epidermis and nectariferous tissue which has vascular bundles(some species were absent)． The modified stomata were present in the epidermal layer and were thought to have a passage in the nectar secretion．However，in a small number of species，there was a structure of small pores in the epidermis；The special-shaped cells which were found to contain polysaccharide and the large parenchyma cells were also observed in the nectariferous tissues．However，the outer morphology of floral nectaries showed greater diversity in number，shape， cuticle sculpture，composition，position and in existence of vascular bundles．These characteristics were different among genera of the same tribe，and sometimes were also different in different species of the same genus．So，they may be of some significance for taxonomy． The floral nectaries of Cruciferae can be divided into three types according to their distribution，morphology and structure：1．Lateral-nectary type：the nectaries were only composed of lateral nectaries；2．Lateral and median nectaries type: the nectaries were composed of lateral and median nectaries，which were separated; 3．Annular-nectary type：lateral and median nectaries united into annular one．The division diviates from the view that was proposed separately by Norris and Clemente and Hernandez. Furthermore, 19 sub-types were divided under the three types. The lateral and median nectary types were considered as primitive whereas the lateral-type and the annular-nectary type were advanced. The evolutionary trends of floral nectaries of Cruciferae are as follows: degeneration of Lateral and Lateral nectary type Median-nectaries→ median nectary
type the combination of Annular nectary type
lateral and median nectarines The possible relationships among the tribes were also discussed according to the distribution of types and sub-types of nectaries in different tribes of Cruciferae.

Key words: Cruciferae, floral nectary, comparative morphology