This tree is outside my dorm. It is a hardwood tree and it's fruiting bodies look limes...but are puffy and full of air, and some strange stringy substance. http://www.botanicalgarden.ubc.ca/forums/attachment.php?attachmentid=35646&stc=1&d=1206653823
It's an oak; the round thing is a gall (look up "oak-apple gall"), caused by a gall wasp, not a fruit. There should be a tiny white larva in the middle of it.
