In 8-quart saucepan combine sugar, water and ginger root. Heat to boiling, stirring occasionally. Remove from heat. Stir in lemon juice. Cool 15 minutes. Remove ginger. Refrigerate lemonade at least 1 hour, or until chilled. (Freeze some of this into ice cubes to use in the drinks, so it won?t be diluted.) Serve over ice, and garnish with lemon slices.