I think that every Corinthian capital (1st photo below) is decorated with the leaves (2nd photo below) of the acanthus plant. Scrolls made from the vines of acanthus plants are also common (3rd and 4th photos below).

                   

Below are photos of a few real acanthus plants I happened to see while walking around Rome. I didn't find one wrapped in a circle like the vines above, but the leaves are easy to spot.

         

The two plants below fooled me into thinking they were acanthus plants. They looked like acanthus to me, but I've been informed that they're different species entirely. So beware, and don't get fooled like I was! Thanks to all who pass corrections on to me.

         

See also:

• My Acanthus Plant photos