Mo. Rev. Stat. § 474.460: Testator surviving devisee, effect.

When any estate is devised to any child, grandchild or other relative of the testator, and the devisee dies before the testator, or is treated as if he predeceased the testator, leaving lineal descendants who survive the testator by one hundred twenty hours, the descendants shall take the estate, real or personal, as the devisee would have done if he had survived the testator by one hundred twenty hours.