Charmoon Richardson was playing hookey from his pre-kindergarten arts and crafts class when he wandered down to a creek and saw a strange, white, shelf-like growth on a fallen tree.

The 5-year-old excitedly hurried the nearest adult to his fascinating find, only to be told: "Oh, it's just an old mushroom."

But Richardson, now 54 and an expert on the 3,000 kinds of wild mushrooms that grow in Northern California, will tell you there is no such thing as "just an old mushroom."

"It was a thing of wonder then - and it still is," he said Sunday as he helped lead a weekend mushroom camp in Occidental. "There's mystery and variety and beauty of form. Every year science is identifying new mushrooms."

More than 100 people had gathered at the CYO-McGucken Center for a mushroom camp, sponsored by the Sonoma County Mycological Society.

Participants learned about mushrooms as food, medicine, dye and even for papermaking and pesticides. They also did some serious mushroom hunting in the woods above the center on Bohemian Highway.

"We were talking for hours, crawling around, looking under trees," said Beth Riedel, a Forestville herbalist, who returned triumphant from the hunt with several bags of mushrooms. "Once you find the right place, it's easy."

Some 225 different species of mushrooms have been identified in the Occidental woods. This year, mushroomers returned to the center with dozens of varieties, including orange candy cap mushrooms that smell and taste like maple syrup and can be used in cookies and cakes.

Also found were black trumpet mushrooms, which grow like underground petunias, and are good sprinkled on top of pizza with a little caramelized onion.

A pile of shiny, daffodil-yellow mushrooms with no known use sat at one end of the center's display table, flanked by bright purple mushrooms called blewits and a cluster of orange, green and brown mushrooms the size and shape of pine needles.

But the mushroom of the hour, the rock star of Sunday's orchestra of mushrooms, was a thick, brown, cylindrical fungus about a foot long and 6 inches thick. Commonly called the quinine fungus, it's under study by drug companies because it seems to possess anti-inflammatory and anti-viral qualities.

"It's one of the hottest fungi going," said Darvin De Shazar, the science adviser to the mushroom association and a biology teacher at St. Vincent High School in Petaluma. "A lot of pharmaceutical companies are working on it."

DeShazar, who is registered with the poison control center, is the person who responds to emergency calls about mushroom poisonings in the county.

Yes, mushrooms also have a dark side.

Out of the thousands of mushroom species that grow in Northern California , only about a dozen species are poisonous.

But that seems to be enough. Every year, people occasionally die after picking and eating wild mushrooms they thought were safe.

But it's easy to confuse edible and poisonous mushrooms. The tasty orange candy cap, for example, has a poisonous twin - the yellow-staining milk cap. The only difference between the two is the color of liquid that flows when the cap is broken.

Richardson's advice is simple: Don't eat a wild mushroom unless an expert has confirmed its identity.

"You don't eat a wild mushroom unless you know exactly what it is," Richardson said. "There is no way to look at a mushroom and know if it is poisonous."

Many victims of life-threatening mushroom poisoning are from Southeast Asia, where the tasty, edible paddy straw mushroom grows. But the paddy straw is nearly identical to the deadly death cap mushroom that grows in California.

Even those who know mushrooms can make mistakes. In 1997, Sam Sebastiani Jr., a 32-year-old member of the Sonoma County wine-making family, died after he accidentally ate poisonous wild mushrooms.