A numerical controller analyzes a program with a command program analysis unit, and determines a macro call or a sub program call with a macro call or sub program call determination unit. According to the invention, the treated plant material has the color and texture of fresh plant material and is substantially free from curling or distortion. The upper plate extends from the lower plate and is bent to be overlapped on the lower plate, thereby forming a heat-dissipating path therebetween. The connecting device is designed as a clamping bracket comprising an upper claw-like section supported on a tubular section of the rack, a second mobile section clamped on the tube, and a third engaging section provided on the mobile section and extending the lever of the mobile section.