Algernon Skinner, 78 of 9 Hancock Avenue, died of gangrene in a leg Thursday at the Medical Center, where he had been a patient since November 7. The funeral was to be held today. He was born at Port Orange, New York, where he had been a farmer until his retirement 20 years ago, when he moved to Jersey City. Mr. Skinner is survived by his wife, Mrs. Nora Skinner (Piatt); his sons, George and Robert Skinner; his daughters Mrs. Winifred McManus and Mrs. Florence Freudenberg, and a stepdaughter, Mrs. Nora Freudenberg.