It looks like a seedling but not necessarily a vine.

Maybe a papaya? They often get into stuff. Search for some pictures.

Here is a link that might be useful: papaya seedling

By the way, nothing like having me guess it wrong then to bring out all those other people to correct me .... :)

Oh, I see you had a picture of the vining habit in this other thread.

Here is a link that might be useful: Better pictures here

Def. not any papaya I've ever seen - & I see plenty
Leaves remind me of mayapple...?

This post was edited by carolb_w_fl on Tue, Aug 20, 13 at 12:12

Certainly not mayapple. The plant in question is a twining vine.

Just for future reference, running two threads on the same question is rather confusing. I see you had an acceptable suggestion on the other one which I wouldn't have seen if esh_ga hadn't linked for you.

I think it is Momordica balsamina. Funny, I saw some the other day, but apart from remembering it started with an 'M' , I couldn't remember the name, until I searched for it.

Momordica balsamina has tendrils this vine is a twiner.

Do the leaves have a papery, rough texture?
Sometimes called Momordica charantia. Stems have twining tendrils and are slender, green, and hairy.

Here is a link that might be useful: Momordica balsamina

This post was edited by costaricafinca on Tue, Aug 20, 13 at 17:30

This plant has twining stems not tendrils,

Maybe a Merremia species, M. tuberosa or the like?

Tonight there is a bud on it, and it doesn't look similar to those of any of the plants mentioned so far.

Yes, the leaves are rough and papery.

Sorry to have confused people with two posts. I'll be sure not to do that again.

Thanks again for all the help. Can't think where I got the seed that produced this plant.

Long shot?

Here is a link that might be useful: Merremia Verecunda / Ipomoea Verecunda