My niece gave me a unofficial looking package of seeds for Christmas that were labeled 'money tree'. The seeds were flat, like a flattened bean -brown and cream striations on them. Any idea what this really is? So far it's quite the prolific grower.

Watermelon?

Maybe. It may be too early to tell what it is. Adult leave are often very different than the juvenile ones.

"Money Tree Seeds" are a popular gift...and a joke/gag gift. The seeds can be from any type of fast-growing plant.

There is another plant called a "Money Tree Plant' - Pachira aquatica aka Bombax glabrum, but the seeds look (to me) more like a striped snail shell and are not flat as you described yours to be.

Please keep taking photos so we can watch your Money Tree as it grows.

The first plant that came to my mind was Money Plant (Lunaria annua) which has the common name of "Money Plant" and has flat, brown seeds.

Another image of a seed can be seen here: http://commons.wikimedia.org/w...
And, a good image of seedlings:

I see the prickly stem and am reminded of melon/watermelon/squash. There is an image in this blog, Our Green Haven/watermelon, image 11 of 18, which has quite a bit of similarity:

http://ourgreenhaven.blogspot....

It will be exciting to watch the little plant as it grows.

Thanks all. These look to match photos of the watermelon seedlings linked above. Definitely not houseplant material and with no free space outside for something like this, I think I'll give the seedlings back to my niece. Thanks.