Cut cucumbers (unpeeled) into slices about 1/16 inch thick. Mix with green pepper, onion, salt and celery seed. Let stand 1 hour at room temperature.
Mix sugar and lemon juice until sugar dissolves. Pour over cucumber combination; add lemon slices and stir to blend. Cover and refrigerate 24 hours.
Makes 5 cups. Store in refrigerator in covered jars. These pickles will keep up to 3 weeks.