Mushrooms of America, Edible and Poisonous (Illustrated Edition) (Dodo Press) (Paperback)

"No general test can be given by which a poisonous mushroom may be distinguished from an edible mushroom. But each species of fungus has certain marks of identity, either in appearance, quality, or condition of growth, which are its own, and never radically varied; none can contain a venomous element at one time, and yet be harmless under other conditions. Like other food, animal or vegetable, however, mushrooms may, by decay or conditions of growth, be unfit for table use; yet in this state no fatality would attend such use. "