La. R.S. 9:1894

If a person dies before the creation of the trust, who would have been a member of the class if he had not died, his descendants shall be considered members of the class by representation unless the instrument otherwise provides. In all cases in which representation is permitted, the division is made by roots. If one root has produced several branches, the subdivision is also made by roots in each branch, and the members of the same branch take by heads.