442.557.  General power of appointment exercisable at death of donee, perpetuities period to run from death of donee. — In determining the validity of limitations appointed in the exercise of a general power of appointment exercisable only at the death of the donee of the power by will or other instrument, or of limitations in default of such appointment, the perpetuities period and any similar period shall run from the death of the donee of the power and not from the time of creation of the power.