Our mystery fungus is the death cap mushroom. If you mistake the death cap for an edible mushroom, you’ll need emergency hospitalization. If you don’t get prompt medical treatment, it will likely cost you your liver or your life.

You were given these clues to help you identify this mystery fungus:

• If this fungus is among us, we’re probably standing under a tree.

• The grinning man with the single-edged blade hopes you don’t know a morel from a hole in the ground.

• "I've got brimmed things made of cloth, and I’ve got collected quite a few.
The balder I get, the more I like what they do."

• If you know your Latin, a Viagra result may come to mind.

The mystery fungus is the mushroom Amanita phalloides, which is widely known as the death cap (and less commonly called stinking amanita or deadly amanita). Whatever you call it, A. phalloides certainly has a sinister reputation. It’s well-deserved, too, since the majority of human deaths and severe illnesses due to mushroom poisoning result from eating death caps.

“If this fungus is among us, we’re standing under a tree.”

The death cap is not a plant or animal, but a member of the fungus family (which is in a class by itself). Though sometimes referred to as a toadstool, the death cap is actually a mushroom. It grows under trees and has a mycorrhizal relationship with them, meaning that it colonizes tree roots and enjoys a symbiotic physical/chemical relationship benefiting both the mushroom and the tree. Most of the fungus consists of a mat of tiny, thread-like mycelia in the soil and wrapped around (and penetrating) tree roots. The part you see above the ground is the flower, which blooms only at certain times – usually September to November. Death caps most commonly grow under oaks or other hardwoods, but can grow under pines as well.

The death cap is present in at least a few National Park System units. Death caps were accidentally introduced to the San Francisco Bay area in the 1930s (apparently through the importation of infested cork oaks) and are probably more common there than anywhere else in the United States. They are known to exist in Point Reyes National Seashore. Presumably, they also grow in Golden Gate National Recreation Area.

“The grinning man with the single-edged blade hopes you don’t know a morel from a hole in the ground.”

The morel (which doesn’t resemble a death cap) is the most popular of the edible mushrooms collected in the wild. The grinning man with the single-edged blade (a scythe, in this case) is the Grim Reaper – that is, he is Death. The symbolization is appropriate, since death caps are lethally dangerous. Every part of this mushroom is poisonous, and a death cap weighing less than two ounces contains more than enough toxins to kill an adult human.

Mistakenly eating death caps, which are actually quite tasty, creates a medical emergency requiring hospitalization and aggressive treatment. The death cap contains potent amatoxins, and alpha-amanitin is responsible for its most deadly effects. Because there are some effective measures of treating early-stage A. phalloides poisoning, a person treated within 36 hours of ingestion can recover with no ill effects. However, a victim who doesn’t get timely medical care is likely to lose his liver (transplants being a last-ditch measure) or his life.

When people who mistakenly eat death caps don’t get prompt medical care, the grim reaper sharpens his blade. He’s patient, knowing that untreated victims take 5-10 days to die. The first symptoms -– violent vomiting and diarrhea, accompanied by severe stomach cramps -- appear after 6-24 hours. These symptoms go away within 24 hours or so, and the victim may then think he’s alright. But he is most emphatically not OK. After three or four days, liver and kidney failure take their toll.

The moral of this story: People who cannot absolutely, positively, infallibly identify edible mushrooms should never eat wild mushrooms.

“I've got brimmed things made of cloth, and I’ve got collected quite a few.
The balder I get, the more I like what they do."

The brimmed thing made of cloth is a baseball-style cap. As the accompanying photo shows, a white or (less commonly) pale greenish, brownish, or yellowish umbrella-like fruiting structure (which can be up to six inches wide) is one of the identifying features of A. phalloides. Though properly termed a pileus, this structure is commonly called a cap. The cap is perched atop a stalk that is as much as five inches tall and has a distinctive cup at its base.

The white gills beneath the cap of A. phalloides is a distinguishing feature that virtually shouts “watch out!” A time-honored rule of thumb is to avoid all mushrooms with white gills. You might want to also bear in mind that the death cap is commonly sticky to the touch (merely handling it won’t poison you) and has a recognizable odor (giving rise to the sometimes-used term “stinking amanita”).

If you know your Latin, a Viagra result may come to mind.

The “phalloides” in the scientific name Amanita phalloides means “phallus-shaped.”

Postscript: Most mycologists seriously doubt that Amanita phalloides is native to the United States. The empirical evidence strongly implies that the death cap was introduced to America accidentally through the importing of trees harboring A. phalloides in their root systems. Another dangerous member of the Amanita family, the deathly white "destroying angel" (A. ocreata), is a native. Like the death cap, the destroying angel has cost dozens of people their lives or their livers.