The invention will be described further by way of example with reference to the accompanying drawings, in which: i I Fig. 1 is a diagrammatic vertical section of a preferred form of wrapping device on the line XX of Fig. 2; i Fig. 2 is a fragmentary diagrammatic section of the device on the line Y-Y of Fig. l; and Figs. 3 and 4 are fragmentary perspective views of the device during a wrapping oper