Abstract: In a baler for forming cylindrical bales, a twine wrapping apparatus comprises a pair of twine guides and a drive mechanism for simultaneously driving the guides transversely of the baler and for feeding two pieces of twine through an opening in the bale forming chamber. In accordance with the improvement, the drive means includes a drive interruption means constituted by a differential for preventing the driving of the twine guides when only one of the twine pieces is being fed into the chamber and wrapped around the bale. The differential includes two pulleys rotatably mounted on a drive input shaft to the twine guides. Each of the wrapping twines passes around one of the pulleys and entrains it for rotation when the twine is being pulled for wrapping around the bale. A planetary gear is rotatably mounted to a support fixed to the shaft and is meshed with annular gears on the inner sides of the pulleys. The twine guides are preferably constituted by a pair of arms mounted on a pivotally mounted support.