I remember seeing seed pods like that in Hawaii. The pods were about 3"-5" in diameter and the actual seed which was about 3/4" x 3/8" long like a bean seed was sort of brown with a darker brown area at the attachment. We would rub the hard seeds on the cement and touch the friction heated seed on each other's arm to cause us to yelp with pain. Crazy kids. I don't know what the tree was called tho.
This one is a bit smaller about 2" - 3" and I'm hoping it's from a Jacaranda tree I didn't have any plant identification books with me. That's the trouble with seed collecting though, sometimes you need to see the long gone flowers to know for certain.
It´s a jacaranda seed pod. I've grown the trees from seed, and they usually germinate well, if you do it in Spring.I usually protect the seedlings for the first winter and then plant them outside.Alex from Portugal