Mix gelatin and sugar in top of double boiler; add water. Place over boiling water and cook, stirring constantly, until gelatin is dissolved. Remove from heat.
Add lemon peel and juice and 1 c. mashed bananas (2 bananas) to gelatin mixture and chill until mixture mounds when dropped from a spoon. Add egg whites and beat with rotary beater until mixture begins to hold its shape. (If necessary, chill briefly until mixture mounds when dropped from spoon.) Spoon into crust and chill. At serving time, peel and slice remaining banana; dip slices in lemon juice. Spread top of pie with whipped cream and garnish with banana slices.