THE PILOT REPORTED THAT DURING TAKEOFF AS THE AIRPLANE ACCELERATED 2/3 DOWN THE RUNWAY THE AIRPLANE LIFTED OFF INITIALLY THEN SETTLED BACK ONTO THE RUNWAY. HE STATED THAT HE CONTINUED THE TAKEOFF AND THE ENGINE STARTED TO SPUTTER. HE STATED THAT THE AIRPLANE REACHED AN ALTITUDE OF ABOUT 50 TO 100 FEET ABOVE THE GROUND AND HE STALLED THE AIRPLANE INTO THE TREES 100 TO 200 YARDS FROM THE END OF THE RUNWAY. THE AIRPLANE WAS REMOVED FROM THE ACCIDENT SITE AND EXAMINED BY THE FAA. THE EXAMINATION DID NOT DISCLOSE ANY ANOMALIES THAT WOULD CAUSED THE MALFUNCTION.