The plant was purchased from a florist, Germany July 2013, and photographed on 24 August 2013.
The flowers show a very prominent UV-signature with a dark centre area and a very reflective circle around the nectaries. The UV-dark area appears orange in visible light and the central UV-bright ring appears white when illuminated with visible light. The latter fact can be hardly seen in the image below, because it is shaded inside the flower.
Visible light: Panasonic Lumix G1, broadband modified; EL-Nikkor 80 mm/f5.6 at ~f11. Baader UV/IR cut filter.
Image reference: CHA_P1100930_130824
Image reference: CHA_P1100933_130824