Orange-Pumpkin Chiffon Pie

In a medium saucepan, mix unflavored gelatin, first addition of sugar, nutmeg, cinnamon and ginger. Beat egg yolks and water; stir into the gelatin mixture. Stir over low heat for about 5 minutes, or until gelatin dissolves. Remove from heat; stir in orange juice, pumpkin and orange peel until well blended. Refrigerate, stirring occasionally, until the mixture mounds slightly when dropped from a spoon. Meanwhile, in a separate bowl, beat egg whites until it holds soft peaks; gradually beat in second addition of sugar until stiff, glossy peaks form. Fold into pumpkin mixture, blending thoroughly. Pour into a graham cracker pie crust and refrigerate until firm, about 4 hours. Combine cream with last addition of sugar and whip to stiff peaks; top pie with whipped cream and orange slices.