From The Food Encyclopedia by Jacques Rolland and Carol Sherman
A nut borne by the oak tree of the genus Quercus. In North America, several species of oak are edible especially the California Black Oak, which gets high marks for taste. The sweetest varieties come from areas around the Mediterranean and W. Asia, called the Quercus ilex var. rotundifolia. In Greek legend, the acorn was a staple food during the Golden Age. Its high carbohydrate content led to its use as a pseudo-cereal by some Native Americans and by Europeans during times of famine. Acorns can also be ground and roasted to make a type of coffee.
