A University of Maine professor riding his bicycle had his left leg amputated after it was struck by the loose blade of a lawn-mowing tractor being hauled by a truck. A university spokeswoman identified the rider as history professor Nathan Godfried. The Penobscot County Sheriff’s Department said that Godfried was riding along Route 2 in Passadumkeag on Sunday when a truck towing a trailer with a mowing tractor on it passed him. Police say the blade had dislodged and instead of being upright was sticking out to the side. The mowing attachment struck Godfried in the leg. A nurse driving past pulled over and stanched the bleeding. Police said they are not planning to charge the truck driver.