Mo. Rev. Stat. § 456.1040: Appointment to deceased appointee or permissible appointee's descendant.

1. An appointment to a deceased appointee is ineffective.

2. A powerholder of a nongeneral power may exercise the power in favor of, or create a new power of appointment in, a descendant of a deceased permissible appointee whether or not the descendant is described by the donor as a permissible appointee and whether or not the descendant of a deceased permissible appointee was alive at the time of the execution of the instrument creating the power or at the time of the exercise of the power.