A poisonous fungus (Amanita phalloides), also called death cap, with a cup-like structure at the base.
From death + cup (Old English cuppe). Named for the lethal toxins it contains and the cup-shaped structure (called the volva) at the base of the mushroom.
The death cap mushroom is so deadly that eating just half a cap can be fatal, yet it's one of the most widely distributed poisonous mushrooms in the world, spread accidentally through imported plants and mulch.
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