Answer: These are most likely seeds. Here is some more information about them, including photos. (You may need to cut and paste the complete url into your browser to make it work correctly.)
This site shows progression in photos from flower through seed, on an evergreen southern magnolia. This site has music, so you may want to turn your sound off.
This site shows a photo of the start of a seedpod on a deciduous magnolia.
I hope this helps.
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