If the vines are still small it's possible that they haven't put out mature foliage yet. Some variety's early foliage looks quite different.

I don't know where seeds are available but Lazy S'S has plants for sale.

Here is a link that might be useful: Lazy S'S Farm

The seedlings were two different sizes and the leaves on one are behaving like the descriptions I've read of Passiflora suberosa growing. The other has Passiflora shaped leaves, but not like that of Passiflora lutea. At this point I will grow them just to see what I got.

Buying seeds even from reputable sources may sometimes get you the wrong plant. However, P. lutea is one of the most variable in leaf that I have seen, second only to P. suberosa and P. tricuspis in my opinion. It is quite possible that both of your seedlings will be different looking, even if they are correctly identified.

Though I am hesitant to ID by leaf photo alone, if you provide us with a picture, we can at least tell you if it is possible that you have P. lutea.

The vines are now large enough that the leaf shape has stabilized. I am thinking it is not a Passiflora.

{{gwi:292363}}

I agree, that doesn't look anything like P. lutea!

They look like P. suberosa, if they get corky bark soon will be those, and the flowers are so tiny, some botanical gardens think suberosa is a waste of space.