I have a volunteer in one of my hanging baskets along with the Bougainville.

http://www.PictureTrail.com/uid3975444

It is about 18 inches tall. The berries have a gooseberry look though not
as big, in that you can see faint strips on the berry. No thorns. It
appears to be very prolific. The flower is about the size of a pencil
eraser, five white petals with a bright yellow center. I don't know if I
should do away with it or propagate it.

Cliff