I am, of course, assuming winter as the season, for in summer the worm "that pierces the liver and blackens the blood" made these regions almost uninhabitable for Europeans.
"Reminiscences of a South African Pioneer"
W. C. Scully
The larger species especially form in this way an abundance of the black fluid, so that it drops from the pileus and blackens the grass, etc.
"Studies of American Fungi. Mushrooms, Edible, Poisonous, etc."
George Francis Atkinson
The saliva of those who use it is red and of a strong odor, and its careless use in time blackens the teeth and makes the breath extremely disagreeable.
"The Medicinal Plants of the Philippines"
T. H. Pardo de Tavera