Our mystery seed this week is a true mystery.
I found this in a "gutter" along a road in Sierra Vista, Arizona. There were no trees or shrubs around that could have produced it. It was probably carried there during a recent rain storm.
As you can see, it is pretty large as seeds go.
If you shake it, you can hear a large seed inside the thin shell-like coating. You can see the seed tip peeking out of the bottom on the right.
Hint: I think the discoloration at the other end, the left side of the photograph, helps indicate what it might be.
Please leave a comment if you recognize this mystery seed.
I will reveal what I *think* it is next Tuesday. Edit: The answer is now posted.