The petiole (leaf stem) glands are the key to sorting this out. P. quadrangularis will have 6 glands on ~90% of the petioles, while P. x decaisneana will have 4 glands on ~90% of the petioles.

This is from Myles' site (see link).

Here is a link that might be useful: Passiflora alata key

hey kiwinut.yip you would think hey...when i got this passi i saw a photo of the supposed flower it was definatly quad....then i noticed that all the leaves had 4 petiole glands and i knew that quad has 6...anyway i got it and know all the new leaves are getting 6 for some reason....the same is happening to a decaisneana i brought through logees...hasnt flowered yet but all new growth are getting 6...but here is the strange thing...i brought a labeled quad from butterfly world but all the petioles are 4?im confused....i know the photos are not of a quad but maybe a hybrid decais.im gonna take photos of the petiole and post them in like 30 min...b rite back

Maybe you have a hybrid that is not an F1 cross, but is from P. x decaisneana crossed back to one of the parent species or another P. x decaisneana. In that case, I suspect the petiole gland rule would no longer apply. Regardless of what you call it, it is still nice.