Fire-scar formation occurs when there is only partial death of the tree bole. It is the result of a complex set of events which depend on environment, fire behavior, and tree sensitivity. Each of these has a number of components of importance and interactions are common. Fire behavior was observed in a model system using metal rods ('trees'), a Meker burner (fire), and a fan (wind) to simulate field fire behavior. Flames tended to persist on the leeward sides of the rods, their heights being influenced by the relative position of rod and flame, rod diameter, wind speed, and gas supply. These variables are sufficient to account for fire-scar formation and other differential effects of fire around tree boles but other factors are also important in the field.