Put this in your pipe and smoke it: A University of Massachusetts professor says the medical marijuana grown by the federal government isn't very good. He wants a permit to cultivate his own pot, saying it will be better for research.

Lyle Craker, a horticulturist who heads the school's medicinal plant program, is challenging the government's 36-year-old monopoly on research marijuana. Craker's suit claims government-grown marijuana lacks the potency medical researchers need to make important breakthroughs.

"The government's marijuana just isn't strong enough," said Richard Doblin, a Craker supporter who heads the Massachusetts-based Multidisciplinary Association for Psychedelic Studies.

A hearing before a federal administrative judge at the Drug Enforcement Administration got under way Monday and is expected to last all week.

Craker's suit also alleges there isn't enough of the drug freely available for scientists across the country to work with.

The DEA contends that permitting other marijuana growers would lead to greater illegal use of the drug. They have also said that international treaties limit the United States to one marijuana production facility.

A lab at the University of Mississippi is the government's only marijuana growing facility.

DEA attorneys defended the government's marijuana, contending its Mississippi growing center provides adequate quality and quantity for legitimate researchers across the country.

"Whatever material is needed could be provided under (the) process that is already in place," said Mahmoud ElSohly, a research professor who runs the cultivation program at the school for government agencies, including a 1,200-square-foot "growing room."

The government's official stockpile at the facility is about a metric ton, he estimated.

"We have quite a bit of inventory," ElSohly said.

Most of it is stored in bulk in barrels lined with federally approved plastic bags.

The most powerful marijuana is stored in a walk-in freezer, part of the facility's storage vault, to maintain its potency.

The National Institute on Drug Abuse oversees the Mississippi facility.

Craker, who has been fighting the government for four years, did not attend the hearing. Doblin, whose group hopes to fund Craker's marijuana growing, said they have confidence in their case, which has the support of nearly 40 members of Congress, including Massachusetts Sens. John Kerry and Edward Kennedy.

"How do you defend the government's case against the public interest that there needs to be more research?" said Doblin, whose group aims to expand medical research on psychedelic drugs, including so-called "Ecstasy" or MDMA. Doblin said he believes there is great promise in the use of "vaporized" marijuana as a health aid.

There was a moment of levity in the DEA hearing room when ElSohly was explaining how the marijuana is sometimes rolled into cigarette form, asking the judge if she understood what he meant.

"I have no idea," replied DEA Administrative Law Judge Mary Ellen Bittner with a smile.

Both sides expect that a decision in the case is months away.