I planted three more tamarind seeds and so far two have come up. I don't think I've ever seen a seed that works quite this way. You can see the brown seeds in the upper right hand corner. They are about the size of a molar tooth.[Double click to significantly enlarge the image.]
Unlike most seeds which send up a stem, the tamarind seed itself gets sent up from the earth. In the August 6 picture (#1) you can see the now green seed has pushed up out of the ground and has a cap of dirt.
Then #2 (August 11, 3:30pm)the leaves are starting to come out of the seed. They have sprouted even further by 5:30 pm (#3).
In Thailand, these trees produce seedpods with a wonderful tootsie roll like fruit inside. You can see full grown trees (in Petchabul, Thailand, the province with the best tamarind) and fruit at this link.