One day an acorn fell from a tree onto a mushroom. The mushroom said "Good acorn, wherefore must you fall onto me?" "Insolent fungus! My forebear is the mightiest of trees, and you are but a dweller in the dung. How dare you complain upon being struck by your superior!" "I meant no offense, good nut. And while I grant that I know not my own ancestry, I please the palates of men, while you do naught but feed pigs."
Hence: Gloriae progenitorum non est gloriae tuum.
Introduction
I found this in Mezeriac's translation.