The flowers of certain plants define a right or left handedness by the sense in which the petals are twisted. Some species and even entire families have flowers of only one particular handedness. There are also plants which produce right-handed as well as left-handed flowers in the same bloom. In the plants of themalvaceae family which belongs to this category, the probability of occurrence of flowers having a given handedness (right or left) undergoes time variations. The possible implications of the right-left symmetry problem of flowers is discussed.