Not sure but this may help....
This article refers to the inflorescence, flower cluster or arrangement of flowers, in petunia as being a cyme
http://jxb.oxfordjournals.org/...
The area under Flower Form in the petunia database appears to show check boxes for inflorescence types rather than flower form. Flower form is above as bloom form - single or double.
I do not know anything about petunias so if this is incorrect, sorry, just trying to help
