Never saw this before, thought it was a fungus, but no; these are former homes of gall wasps who specialize in setting up housekeeping on the undersides of oak leaves. Taken yesterday. Latin name Cynips quercusfolii. Say that and you've said a mouthful.
Unless there's a hole in the side of it, I think the wasp larva is still inside there. You could carefully cut it open to find out.
ReplyDeleteWOW! That's sooo neat! What beauty and great form! Too amazing :)
ReplyDeleteChris