Mortartube (unique name) isn't far off. In the early days of airplane building, a single piece of (usually) Spruce was used as the main spar and carried thorugh the fuselage for the primary support structure for both wings.
Later, it became more efficient (and easier to repair) wings that are attached to a structure within the fuselage. In WWII (actually in the 1930's) Douglas manufactured the venerable C-47/DC-3 (I think you Brits called it the
Dakota was bolted on each side through flanges that ran around the top and bottom of the wings, as seen
here ... (sorry for the long URL.)
The First American jet transport (Boeing 707) was designed so the wing would flex through an arc of about 5 feet in flight. The Boeing 747 wing flexed nearly 20 feet seen in this photo:
http://www.airplane-pictures.net/image5856.htm l . This could only be achieved by the attachment of the wings to the center section. Thanks for the question!