That day he identified 33 separate species of mushrooms, ranging from edible to hallucinogenic to poisonous, but he says there are believed to be three to four million different species in the kingdom Fungi, and only 10 percent of them have been named.
When he spotted a mushroom that stumped him in the park, he whipped out his phone and took a photo to compare with reference books and online sources later on. It's all part of the thrill of discovery.
And now that it's raining, it's mushroom season on the Peninsula, when the spore-bearing fruiting bodies of fungi pop out of the ground or from decaying trees, sometimes appearing overnight or enduring for decades.
Stopping on a public roadside, Caughey pulled out a specialty mushroom knife, which has a curved blade, to harvest a specimen to inspect under his microscope at home. He could send any mystery mushrooms to a lab for DNA testing, but at the cost of hundreds of dollars, that can add up quickly.
He was delighted by his first sighting this season of Lactarius rufulus, or Southern Candy Cap, which he describes as tasting like maple syrup when dried (he has a dehydrator). The specimen may end up as a tasty treat at his monthly meeting of the Mycological Society of San Francisco, where members snack on mushroom-related foods during show-and-tell and lectures.
Caughey mans the toxicology table at the society's annual Fungus Fair. He calls himself a "physician scientist, a molecular biologist, chemist," and "amateur mycologist."
He retired last year and is now a professor emeritus at University of California at San Francisco, where his focus was on pulmonary, critical care, allergy and sleep medicine. His interest in fungi mushroomed some 30 years ago in New Hampshire when "we were living off the grid one summer and I was just surrounded by mushrooms," he says.
Curiosity led him to reading about them, attending meetings, and going on forays. Last fall he and his wife went on a mushroom-collecting trip to Sicily. The object was to see what grows around Mount Etna, and the group the couple traveled with found 250 species.
Throughout the late January walk in Woodside he spots a type of mushroom found on rotting wood all over the world in horizontal bands of ring-patterned fans, Trametes versicolor, or Turkey Tail.
In China and the Far East, he says, they are used medicinally for immune-boosting purposes in teas and tinctures.
He identifies two large, fleshy orange-colored mushrooms that are sometimes mistaken for chanterelles: Omphalotus olivascens, or Western Jack O' Lantern, and Phyllotopsis nidulans, or Orange Mock Oyster. The first glows in the dark and is poisonous, whereas the second smells like rotten eggs and is "mildly toxic."
Near the Greer Road park entrance he spies a Galerina marginata, or Deadly Galerina, sprouting out of a dead coast live oak.
"People have poisoned themselves on these looking for hallucinogenics," Caughey cautions.
When he gets to the fallen tree in the East Meadow that is hosting several clumps of mushrooms textured like coral, Hericium corraloides, or Comb Tooth, he is clearly excited, using his walking stick to point out the features of what he calls a "charismatic mushroom."
He pulls out the extended mirror he carries to check out the undersides of various fungi for pores or gills, and exclaims, "It is delicious ... to me this is a beautiful mushroom!" adding that his daughter's boyfriend likes to use the white delicacy as a pizza topping.
"There are people who take chances, but I just stay away from any category of mushroom considered lethal; I'm very conservative," he says.
After eating about 40 different species over the years, he has gotten a stomachache only a couple of times, he says.
His theory is that it's OK to take a tiny taste and then spit it out. "No mushroom will poison you unless you really eat it, and then it takes several days," he says.
"Six hours later you get diarrhea. The dangerous thing is the honeymoon period when you feel good again, and then everything shuts down in three days, and you're gone."
He recalls the December 2017 news headlines of an incident when doctors had to treat 14 people who became severely ill after eating wild mushrooms foraged in Northern California mountains. Three ended up with liver transplants, including a toddler who also suffered permanent neurological damage.
The most likely culprit was the Amanita phalloides, or Death Cap, which Caughey says was introduced here in the 1930s on nursery stock imported from Europe, and can be found where coast live oaks and cork trees grow.
He hasn't seen any yet so far, but usually runs into "hundreds" of Death Caps in his yard, near the Pulgas Water Temple, and in the watershed near Filoli, where he used to lead mushroom hiking tours and helped train the current batch of nature docents.
For all amateur mycologists he recommends reading: "Mushrooms of the Redwood Coast" by Noah Siegel and Christian Schwarz; "California Mushrooms" by Dennis Desjardin, Michael Wood and Frederick Stevens; and "Mushrooms Demystified" by David Arora.
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