A policeman arrested in New York City was charged with selling marijuana he had grown behind the police station in Central Park. The officer, Ptl. John Gardellis, 26, was suspended pending the outcome of the case. A spokesman for the police narcotics division, Lt. Paul Murphy, said Gardellis was arrested on information supplied by four undercover policeman after a lengthy investigation. Murphy said Gardellis, a policeman for three years, grew marijuana plants behind the police station only 10 feet from the stables where police horses were kept. He said there had been 8-12 marijuana plants there, and they were about three feet tall.