Mystery red berry with white "casing"

These grow on a large bush--7 feet in diameter. The small (1-2 cm) berries appear white at first, but then the white sepals (?) open, rather like popcorn, to reveal a smaller red berry inside. You can view a picture of them with a leaf at:
http://gallery.me.com/rwconner#100134
The white sepals have dried and folded back along the stem, but you can see how they (3 per berry) would have encased the red berry.

I have found only two bushes of this type and at different times in the Morton Arboretum near Chicago.

Any ideas?

 

Celastrus.

 

Thanks!

 

http://plants.usda.gov/java/profile?symbol=CESC
C. scandens?

 

Presumably, thanks. My specimen was quite small. Possibly the Arboretum is trying to prevent its spreading.