To prepare fruit. Wash and peel fruit. Cut peel into thin strips. Add cold water and simmer in a covered pan until tender (about 30 minutes). Drain. Remove seeds and membrane from peeled fruit. Cut fruit into small pieces. To make marmalade. Add boiling water to peel and fruit. Add sugar and boil rapidly to 9 degrees above the boiling point of water (about 20 minutes), stirring frequently. Remove from heat; skim. Pour immediately into hot, sterile canning jars to 1/4-inch from top. Seal and process 5 minutes in boiling water bath. This recipe yields 3 or 4 half-pint jars.