C3/C4 plants

[Sushil Kumar Rijhwani]

Hi There,
        Does anyone out there know of a reference which classifies
plants into C3 and C4 types? I specifically want to find out about the
plant Periwinkle(Catharanthus roseus) belonging to family Apocynaceae.

        please respond to rijhwani at owlnet.rice.edu

Thanks

Sushil K Rijhwani