I am wondering if anybody knows what this is? 
At first I thought it was some kind of seed pod, covered in fungi.  But then it started to GROW at about an inch and a half a day after I brought it inside.
The inside part that is elongating is almost structured like styrofoam or sponge, but it is rigid. That was originally surrounded by a dark green covering that appeared like some kind of nut might look, but it was soft.  (It is now still in place, but liquid in most places.  And hardened like clay in others).  That was covered by a soft, cream color layer and on top of that was a brown earthy substance that smelled like fungus.  Now that the inside has elongated and the green part has turned to liquid, it just stinks. What is it??  Found under a school yard picnic table in deep shade, damp ground.