Identification: Need Hawaiian plant ID please.

This plant was a kidney bean (shaped and colored) seed in a long pod of many seeds. It was found in Hawaii.
It folds it's branches/leaves up every night. Amazing- timed with the sun.
Can you help me identify it?
I have included a night and day picture.
Thanks,
Kerry

 

One of the Sennas, I'd guess. Which one is tough to say without seeing flowers - it's a big genus.

 

I don't think it is a senna. The seeds were very different as were the pods from senna I have found online...
Thanks for trying...
Kerry

 

Senna, as I said, is a huge genus. There are 250 species, and they used to include Cassia as well, which is another several hundred.