I am also researching a Magnolia and was reading another post relating to spelling of the name. That post suggested a correct spelling of Magnolia x soulangeana. Was that post relating to another Magnolia? Just curious and trying to collect the information.
I guess you are referring to: http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=76499&highlight=soulangiana It is correctly spelled with an "e" but is a hybrid, so: Magnolia ×soulangeana on IPNI And GRIN http://en.wikipedia.org/wiki/Magnolia_%C3%97_soulangeana Chinese botanists have split Magnolia into several genera, so it is listed as Yulania ×soulangeana (Soulange-Bodin) D. L. Fu on the Flora of China All referring to the same taxon.
On the page discussing the family the same treatment also has two paragraphs detailing problems with Magnolia remaining broken into a bunch of different genera, with the first paragraph citing multiple genetic studies pointing toward it being considered a single genus. http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=10530
