When a visitor arrived at his Arizona home recently, wheezing with a troublesome cold, Dr. Andrew Weil rushed to his extraordinary medicine cabinet—the botanical pharmacopoeia that grows wild in the desert. Spotting a small blue-green shrub called porophyllum, he yanked out a few stalks and brought them back to his kitchen. "The Indians have used this for centuries to treat colds and pneumonia," he said, brewing the branches into a tea. "It's a little unconventional, but it works."

The same could be said of Weil himself. At 38, he has an M.D. from Harvard and academic appointments at both his alma mater and the University of Arizona. Yet he keeps no office hours and does not teach regular classes. Instead, as president of the Beneficial Plants Research Association, a nonprofit organization he co-founded last year, Weil is an explorer in a botanical wonderland. Like many explorers, he is a missionary. "We want to educate people about natural products," he says. "We want to introduce new plants that will improve people's lives—new fruits, natural insecticides, nontoxic food colorings and safe psychoactive drugs."

Among his enthusiasms is the purplish mangosteen, a southeast Asian fruit the size of an apple. "It's white inside with crimson veins," he reports, "and it melts in your mouth like ice cream." Another favorite is the high-caffeine coffee substitute yoco, a bark extract that is brewed into a beverage by Amazon Indians. "I think coffee is a lot more irritating to the stomach than other caffeine drinks," says Weil. "But yoco seems nonirritating and takes away hunger and thirst." Weil is equally keen on the scalding hot chili peppers cultivated by the Cubeos, another isolated Amazon tribe. About twice a year Weil travels to Colombia, trying to help the Indians organize a chili-growing cooperative. "We could market the chilies in the U.S. on the basis of their being tastier and hotter, as well as being organically grown in the Amazon jungle," he maintains. "By doing so we would give the Cubeos the economic leverage to resist cultural domination."

None of these projects, however, is closer to Weil's heart than his search for a medically useful extract of coca. Though known principally in this country as the source of cocaine, the coca leaf is chewed by Indians in the South American highlands for energy, a sense of well-being and relief from a wide variety of gastrointestinal ailments. Out of a start-up budget of $370,000 solicited from foundations and individuals, Weil's research organization is seeking $150,000 to develop a coca-derived prescription drug in lozenge or chewing-gum form. "It would have the color, odor and flavor of coca—everything in the leaf but the cellulose, which is inactive," says Weil, who uses a rarely granted government permit to import 100 pounds of coca leaves annually. Ultimately, he is optimistic that tests will establish that coca is useful in the treatment of gastritis, peptic ulcers, hypoglycemia and other ailments. He also believes that coca is safer than cocaine while providing some of the same consciousness-altering qualities. "The dose of cocaine in coca is low, being diluted by inert material," he explains. "There are also vitamins and minerals in it. And it's hard to abuse, because you can't snort a coca leaf."

Starting with hypnosis as a child, Weil has always been intrigued by changes of consciousness. Brought up in Philadelphia, where his parents ran a millinery supply store, he enrolled at Harvard in 1960. Like many freshmen there, he experimented with mescaline; unlike the others, he continued experimenting until he found a career. In his just published book The Marriage of the Sun and Moon (Houghton Mifflin, $9.95), Weil argues that life becomes "sterile" without consciousness-changing highs. He stresses, however, that such experiences are possible without drugs. In 1970, for instance, on a visit to a Sioux Indian reservation, he discovered the consciousness-altering powers of the sweat lodge, an intensely hot sauna generating temperatures approaching the boiling point. "I'm a sweat freak now," he says. "I think drugs are a perfectly valid way of getting high, but they do tend to reinforce the illusion that these experiences are coming from outside you and not within you. People become dependent on drugs for that reason."

Weil's first scientific drug study was a Harvard undergraduate project in which he acted as his own guinea pig, studying the consciousness-changing properties of nutmeg. "It's a real desperation drug," he recalls. "I tried the spice a number of times and it was horrible. I would eat half a container, feel nothing and then go to sleep. The next morning I couldn't get out of bed." Later, while attending Harvard Medical School, Weil gained a precocious notoriety by conducting the first controlled human experiments anywhere with marijuana. The federal government obligingly provided the marijuana, but Harvard refused to allow the study on its premises, so Weil moved his experiments to Boston University. Although Harvard retaliated by threatening to withhold his degree, Weil eventually got it anyway. He also made the front page of the New York Times by refuting several widely held but previously untested beliefs—for instance, that marijuana dilates the pupil of the human eye and lowers the body's blood sugar level. "In the light of research since then, our experiments were very primitive," Weil observes, "but everything we found has been confirmed."

Graduating from med school in 1968, Weil had no interest in becoming a traditional physician. "I felt that most of the techniques I had been taught, especially the administration of very strong drugs, caused more harm than good," he explains. "I felt there must be ways of treating illness other than a vast overreliance on medication and unnecessary surgery." After a disappointing year at the National Institute of Mental Health—"I was supposed to coordinate marijuana research, but I just sat in a windowless cubicle with nothing to do"—he won a fellowship and traveled through Latin America, finding and tasting unusual plants.

Weil's eat-now-and-ask-questions-later approach sometimes brought painful results. In Colombia, after downing two cups of yagé, a bitter hallucinogen derived from a climbing tropical plant, he was overwhelmed by vomiting and diarrhea. At a market in El Salvador he bought cashews and tried to crack open the leathery shells in his mouth. It was a costly mistake. "A layer of tissue came off my tongue and lips," he recalls. "I couldn't eat or drink for two days." (He later learned that the nuts' caustic covering is the reason they are not sold unshelled.) Still, Weil's research in Latin America helped establish his scientific credentials. "Andy is well recognized for his work on coca and on the use of yagé," says Richard Schultes, director of the Harvard Botanical Museum. "On the popular side, his contribution has been to draw attention to the great potential of plants as medicine."

Soon after returning from his South American travels in 1973, Weil stopped in Tucson for a brief visit. A wheel bearing on his Jeep shattered, and during the six weeks that he waited for repairs he fell in love with both the Arizona desert and Mahina Drees, 39, a folk singer and agriculture researcher. Five years ago Weil and Drees moved into a stone house at the end of a teeth-rattling unpaved road on the outskirts of Tucson, surrounded by towering saguaro cactus. "If you call traveling six months a year being settled down, he settled down with me," says Drees with a laugh.

When he is not addressing his peers at medical conferences or studying with Indian shamans in the jungle, Weil conducts a part-time, informal medical practice at home. "Because patients must be willing to come over the road, those who arrive tend to be highly motivated and to have unusual medical problems," he says. His prescriptions usually range from stimulant teas to yoga exercises and biofeedback. But he is no longer a doctrinaire radical in the matter of shunning conventional remedies. "I used to think people got sick because they want to," he remembers. Then, while watching a sun dance on an Indian reservation in 1971, he stared at the sun off and on for four hours. His visual field became "a mass of kaleidoscopic colors," and though the condition vanished after several months, he was left with reduced confidence in the power of the mind over matter. Now he sometimes coaxes his reluctant patients to accept mainstream medical treatments. "One young woman came to me with a cancer-like syndrome that had reached her liver and made her secrete a hormone that affected her heart and blood vessels," he recalls. "She was very resistant to orthodox medicine and wanted to try yoga. What she needed was open-heart surgery—and I got her into it." Another woman called just after returning from the Himalayas, where she had spent her time getting high on cobra venom. "She was reading tarot cards and eating only nuts and berries," Weil remembers. "She said people's faces looked like skulls to her." Given that remarkable symptom, did the doctor prescribe yoco and sweat baths? "No," he says, "I told her to stop reading fortunes and to start eating meat."