Beware the Jabberwock, my son, The jaws that bite, the claws that catch, Beware the Jub-jub bird, and shun The Frumious Bandersnatch. -- Lewis Carroll The forest reeks of foul odors. Something venomous lurks under every log. And if you see a patch of buttercups, don't walk -- run.

Poisonous: that's the word. Ranger Bill Eaman, a dog-eared copy of "Peterson's Field Guide to Wildflowers" tucked under his arm, dispensed a compendium of "don'ts" the other day as he led an expedition through the brambles of Rock Creek Park. The hardy souls who followed him were cruising for a bruising.

"Leaves of three, let them be," Yeaman warned, pointing to the vines that spread across the trail. "Three on a stem, don't touch them." There was a dark cast to his eyes. "Careful, folks. That's poison ivy."

Yeaman, a 30-ish Montgomery County native, had gathered everyone together at the entrance of the Nature Center -- about 15 people, most of them in heavy boots -- and promptly got down to business. "This here," he said, indicating a coiled snake with gaping jaws, "is a copperhead."

It mattered little that the reptile was trapped in a glass case, and quite dead. Its markings faded by the sun, it was formidable nevertheless. "There might still be some of these in the park, though there haven't been any sightings in more than 10 years," Yeaman allowed.

There was excitement enough, however, Moseying around to the other side of the building, Yeaman found a fibrous clump hidden under a shingle. "This," he announced, "is a nest of bald-faced hornets." Murmurs of awe pulsed through the group, which kept a respectful distance.

Suddenly one of the nest-dwellers put in an appearance, diving from the shingle and rolling and yawing through the adventurers. People variously scattered or went into a crouch. At length the creature disappeared.

"Oh there it is," a photographer along for the expedition said pleasantly to a reporter. "It seems to be going after a caterpillar on the back of your shirt."

"Get it off me, please," the reporter replied evenly, The photographer stayed put. "Get it off me, right now." There was frenzy in the voice and a wild flapping of arms, as all pretense of rational thought vanished into the breeze. The photographer obliged. Bill Yeaman looked worried.

The rest of the excursion, which lasted two hours, is somehow hazy in the memory. But Yeaman did point out such noxious plants as the buttercup (deceptively appetizing), milkweed, may apple, pokeweed, jack in the pulpit and devil's walking stick -- this last a thorny affair oozing evil goo. "It'll put bumps on your skin," Yeaman said.

In a glade, the group happened on an ailanthus weed, otherwise known as a Tree of Heaven, the Yeaman broke off a leaf and passed it around. "This plant is famous for its ability to absorb automobile pollution and thrive," he said. "Smells like kerosene, doesn't it?"

Finally came a triple-play of poison: a dead honey bee, being methodically consumed by a small crab spider in the blossom of a black locust flower.

"Hmmm," Yeaman said. "You don't see that too often."