A. That’s a very good question. Most of the illicit material in the 1960s came from Mexico. So, in collaboration with the D.E.A. and the Mexican government, we acquired those seeds. Later, we acquired others from Colombia, Thailand, Jamaica, India, Pakistan and places in the Middle East. That permitted us to study chemical and botanical differences. By 1976, we were growing about 96 different varieties.

Interestingly, that led us to see that there was only one species of cannabis. It had always been thought that there were many. But you could see that the chemistry of this plant is the same qualitatively no matter where it comes from. What makes each different is the relative proportion of the different chemicals in there, which doesn’t make a different species. It’s really the same species, but different varieties of it. The different types of varieties hybridize very easily.

Q. DOES THIS MEAN THAT ONE COULD MAKE GENETICALLY MODIFIED CANNABIS?

A. Yes. Absolutely. That actually has been the trend over the years in the cultivation in the illicit market, and also in the legal market, where we are doing genetic selection, where we select specific materials that have the genes that produce higher levels of THC or some of the other ingredients.

Q. SO OUT THERE IN RURAL NORTHERN CALIFORNIA, HAVE THEY BEEN IMPROVING THEIR CROPS WITH MODERN GENETICS?

A. They have been doing genetic selection for years. You can see the potency keeps going up. In the 1970s, the seized marijuana had probably 1 percent or less of the active ingredient. Now, it’s about 8 percent, on the average.

Q. HOW DID YOU COME TO YOUR UNUSUAL SPECIALTY?

A. The honest truth is that it began out of necessity. In 1975, while I was in my last year of graduate school in natural products chemistry at the University of Pittsburgh, the Lord provided me with twin daughters. My graduate student stipend was already over, and my adviser said, “You need to quickly find a job.”

So he recommended me for a postdoctoral fellowship at the University of Mississippi’s Research Institute of Pharmaceutical Sciences. My first job here had to do with poison ivy. Then a better-paying position opened up at the Marijuana Project, and I moved to that. I liked the research, and I got on well with my supervisor and mentor, Dr. Carlton Turner, who later became the director of drug abuse policy in the Reagan White House. So, this work, it just happened.

Q. DO YOUR NEIGHBORS EVER KID YOU ABOUT YOUR JOB?

A. My daughters, when they were in grade school, the teachers would ask them, “What does your father do?” And they’d say, “He grows marijuana.” And the teachers’ eyes would grow wide. After a while, my daughters said: “He works at the University of Mississippi. He’s a professor.”