Аннотация:[Russian text published in Uspekhi Sovremennoi Biologii, 2021, Vol. 141, No. 1, pp. 50–65]The contemporary evolutionary developmental biology includes molecular phylogeny, studies on morphology and morphogenesis, genetics, and genomics. The most reliable conclusions about main trendsof f loral evolution can result from investigations of highly polymorphic group, which is precisely characterized from the positions of both modern systematics and molecular developmental biology. The legume family, Leguminosae, is a group of such kind. It demonstrates an outstanding variation in f lower structure. Theancestral floral structure in this family includes monosymmetry, pentacycly, with pentamerous perianth andandroecium, and a monomerous gynoecium. However, distinct evolutionary lineages resulted in origin of polysymmetric perianth, different patterns of staminal reduction or polymerization, as well as multicarpellate gynoecium. A strikingly high level of homoplasy is found in Leguminosae. Besides the existing evolutionary tendency to stabilize floral structure, the exact “instability syndrome” evolved repeatedly, associated with a polysymmetry and characterized with a highly variable number and position of floral organs.