On July 13, 1995, at 1524 central daylight time, a Cessna 172L, N3967Q, was substantially damaged during landing near Porter, Texas. The private pilot was not injured. Visual meteorological conditions prevailed for the personal flight. In an interview with a Federal Aviation Administration inspector, the pilot reported that he was practicing touch and go landings. While on the downwind leg, in preparation for the fourth landing, the pilot stated that the engine "misfired" so he "turned back to the runway." The aircraft "landed long," approximately half way down the runway. Following touchdown the aircraft ran off the end of the runway and traversed across a drainage ditch and subsequently struck several trees. Examination of the aircraft revealed structural damage to the left wing and the right wing separated from the aircraft. No anomalies were found that could have accounted for the loss of engine power.