There’s an old Yankee saying: There are old mushroom pickers and there are bold mushroom pickers, but there are no old, bold mushroom pickers.

If you’re of a philosophical mind-set, you might wonder why Mother Nature produced thousands of mushrooms of varying shapes, colors and sizes, and created a few of them so delicious that we’re willing to risk our lives by mistakenly eating any one of the poisonous variety. Why can’t they all go right into the frying pan?

Last Saturday afternoon, a group of 40 people assembled in the Polly Hill Arboretum barn to hear fungologist — yes, it sounds insalubrious but it means a mushroom expert — Marlene Snecinski introduce us to the profoundly fascinating world of wild mushrooms.

Ms. Snecinski is a scientist, so a mushroom that could be safely sautéed in an omelette isn’t necessarily any more interesting to her than a purple specimen with removable gills that could fatally ruin a pot of goulash. A vocal minority of people in the group continually piped up at the sight of a new specimen, “Can we eat it?” The answer was usually “No.” There is, too, a wide variety of harmless mushrooms that cook up mushy and tasteless, so there’s no point in bothering with them from a culinary point of view.

Some of the group enjoyed previous knowledge, particularly pertaining to mushrooms found on their own land. Accordingly we had an immense variety of types arranged on a long table, enough to make us glad there would be no exam at the end of our three-hour course.

Ms. Snecinski, with shoulder-length strawberry blond hair, wearing a neon green tank top and a fetching brown and orange necklace of large beads, told us she’d acquired her house in Vineyard Haven in 1985. Her job as an engineer led her to a continuing interest in the sciences, and the first one she adopted on Island was birding. She has also been involved in the slow cooking movement for 25 years. One of her slow cooking friends served her a delicious mushroom side dish. “I found it in the woods,” the woman explained.

That was enough to spark a new obsession for Ms. Snecinski. She began following woodland paths looking up for birds and down for mushrooms. “I started to get a painful crick in my neck,” she said, “so I began to concentrate almost exclusively on mushrooms.”

One of the magical properties of mushrooms is that a threadbare landscape can yield an amazing and diverse crop after a single night’s rain. One of the edible mushrooms on the Island are morrells, which appear in sweet soil such as that found under apple trees or, elsewhere, under elms. The western part of Connecticut, for example, is rich in limestone which yields a sweet soil and a vast crop of morrells.

Chanterelles are fairly common here in the early summer. They’re yellow or orange and have ruffled layers slightly suggestive of ballet tutus. They have gill-like ridges underneath the cap, tapering seamlessly down the stem. A mild, peppery taste makes them a popular food dish. There also exists a species called false chanterelles which were once considered harmful but now are known to be safe but tasteless. And yet, who knows, with enough olive oil, tumeric and cumin, they could sponge up flavor the way tofu does.

Our soil, especially our lawns, are covered with a deadly strain of fungi called amenitas. “They look so innocent,” remarked one of the troopers and, indeed, they’re mostly small and round like cousins of our supermarket button mushrooms. Ms. Snecinski cut one out of the ground and showed us the bulb underneath: “If it grows out of a bulb it’s very poisonous.” Good to know.

After an engrossing hour-long introduction, we were handed loops (much like jewelers wear to examine diamonds) and set off into the arboretum hinterlands. Ms. Snecinski, for her excursions, brings a wire basket, paper bags, a knife, a notebook and her own loop. She also often carries an egg carton to separate the mushrooms. “Some of them give off a milky discharge and you don’t want this combining with dryer fungi.”

Another common mushroom in these parts is the puffball, which rests round and meaty looking on the ground. They’re edible if they’re white in the middle and of a marshmallow consistency. They grow in meadows and Ms. Snecinski has a favorite dish for them called puffball Parmesan.

An edible mushroom that our fungologist fancies is the orange chicken, and its cousin, the bleached-out hen. The ritzy layers do indeed form a size approximate to a chicken, so a single sample will provide a full meal. Chicken and hen mushrooms have a long season, and they grow on dead wood. It’s important to cook a fresh one right away before it has a chance to get tough and woody. The species also has long been used in a tea as an immune system booster.

On our escapades through the forest, we came upon shelf mushrooms on trees and logs — too tough to eat —the angelic-looking demon amenitas; sueillus (“cooks up mushy”); the lotus-like gregarious (“too bitter”); rumaria, a coral-like fungus (toxic); rushula, with gills that break off underneath (“not worth messing with; taste can run from good to mediocre”); and the small yellow honey mushroom to which some people are allergic so it should in all good conscience be foresworn. We also found a slime mold which was shown to have wriggling parts under our scopes, a bat-wing shaped slime mold, and a red-nub capped agaricus, some of which are poisonous, although the meadow and horse variety are both edible and good.

It’s a complicated and treacherous field. Ms. Snecinski recommends foraging with a club so that at the end of a two-hour hunt, the crew can lay out its finds, open up field guides (Ms. Snecinski’s favorite is the Audubon), and gain some consensus on what sits before the group, and which of the catch belongs in a pan.

Until true expertise is obtained, this reporter’s advice comes directly from her mother: “Never eat anything found in the wild.”

Unless someone has dropped an unopened Hershey’s bar.