You may use either frozen or fresh blueberries. If frozen thaw berries until most of ice has disappeared. Drain off juice, measure, and add water to make the amount of water called for in recipe. Stir into a mixture of sugar, tapioca, and cornstarch in saucepan. Heat rapidly until thickening is completed. Boiling is not necessary. Set aside to cool. Then add lemon juice and blueberries. Pour filling into pie pan lined with pastry. Add top crust, seal and flute rim. Cut slits in top crust. Bake in 425 degree oven for 30 minutes or until nicely browned. For a browner crust, bake on lowest shelf. When blueberries are in season you may want to make up a double or quadruple batch and put in freezer for pies later.