This fruiting fungus looks plenty healthy, which doesn't bode well for its Turkey Oak host.
I don't know if it's fungal, but some pathogen is afflicting the Cucumber Tree, and other Magnolias in the Park. This fruit should be shaped like a cucumber (hence the name), but it's badly distorted. I'm worried about this tree.
Some trees have chronic diseases that aren't really a big problem. The darkening Hackberry fruits above are ripening normally. The green nodules aren't fruit, but the result of a mite-borne fungus. The condition is so common it's considered an identifying characteristic.
There's nothing wrong with this Osage Orange. It's just weird. It stays green, even when ripe, and definitely wins the contest for the fruit which looks most like a Martian's brain.
Well, there's a harvest basket full for you. I'll let you know if anything else good turns up, or, more accurately, falls down.
Back to the Arboretum.