Explanation

Perianth Onion flower have 6 tepals in two alternate whorld of three each, polyphyllous Androecium Six, stamens in two whorls of three each opposite the tepals; antipetalous Gynoecium Tricarpellary, syncarpous ovary, trilocular with 2 ovules in each locules. So, from the description it is clear that the given floral diagram is of onion plant