Mix the ingredients and press them into a 9" pie plate. Bake in a preheated 350F oven for 10 - 12 minutes until lightly browned. Place on a rack to cool.
Combine the 1/2 cup sugar, water, egg yolks, lime juice and gelatin in the top of a double boiler. The water in the bottom of the double boiler should be boiling. The upper container should be over but not touching the water. Cook the mixture until it thickens.
Add the grated lime peel.
Refrigerate the mixture until mounds are formed when dropped from a spoon.
Beat the egg whites until stiff but not dry. Gradually fold in the 1/3 cup of sugar. Fold this mixture lightly into the chilled lime filling until evenly blended. (Do not over mix or your pie will be dense rather than fluffy). Turn the mixture into the prepared pie crust. Chill until set, normally several hours or overnight.