The motto of Minnesota's MacMillan family, heirs to the Cargillfortune, could be that the only good mouth is a closed one - unlessit happens to be eating a grain-based food product.

One of Minnesota's wealthiest clans, the MacMillans also havebeen one of its most doggedly secretive. But the recent publicationW. Duncan Macmillan of Wayzata, offers the closest look yet at theprivate lives behind the largest privately held company in theworld.

Anyone hoping for a scandal-laced tell-all will be sorelydisappointed. In fact, sensational or otherwise, information on thecurrent activities of any Macmillans still living is scant. WhitneyMacMillan , Duncan's cousin, is generally credited with runningCargill very well in the 1970s through mid-1995, when the companyrealized much of its growth.

This book primarily paints portraits of Duncan's grandfather,John Hugh MacMillan , and father, John H. MacMillan Jr., who were themost instrumental figures in shaping what today is a $51 billionCargill business, and laying the groundwork for the company's statusas a dominant player in the international food market anddiversification into finance and other business arenas.

As portrayed in the book - published by theMacMillan -bankrolled Afton Historical Press - both men were theright leaders at the right time. John Sr. was a cautious,by-the-numbers type who revived a company foundering from thedepression of the 1890s, and John Jr. was a relatively bold,experimental type whose instincts brought further expansion in thegrowth boom of the 1950s.

Even though Duncan MacMillan can afford to throw things away,he "never much liked to," he said in a recent interview at his homein Wayzata. Excerpts from his collection of family letterscomprise the most interesting and revealing inclusions in thebook.

Today, no MacMillans are active in the company's day-to-dayoperations, although several sit on its board. Neither Duncan norhis older brother John Hugh III, who lives in Florida, ever emergedas key leaders of Cargill. Those roles were filled by his cousinsWhitney MacMillan , who ran the family business for nearly 20 yearsbefore retiring in 1995, and his brother, Cargill MacMillan Jr.With an estimated personal worth of $975 million each, the threeheirs are tied for the position of 5th richest Minnesotan, accordingto Forbes magazine.

"I don't think the rest of the senior members of the familyare all too happy about the book. I didn't ask. The youngergeneration is OK with it," he said.

None of Duncan's four daughters live in Minnesota, but theywere in town recently for a company shareholders' meeting.

For Alexandra Daitch, the youngest at 36, the book "reallyreconfirmed what great and different thinkers my grandfather andgreat-grandfather were - the first focused on grades andperformance, the second on personality and character - and how rightfor their respective times both of their management styles were."

Her sister, Katherine, 44, said the book made her feel "proudof her heritage, to know that I was raised under that roof. Theknowledge of the past helps to improve the knowledge and the livesof the future generations."

The rest of the MacMillans remain as mum as ever where publiccomment is concerned. When reached by telephone at his home betweenan Arctic fishing expedition and a visit to his Colorado retreat,Cargill MacMillan Jr. said he had not yet read the book, so hecouldn't comment. None of the other family members returnedcalls.

Charmed life

Duncan, 68, has a reputation as a more eccentric, at timesflamboyant, personality than his cousins. An avid athlete, hecurrently is best known as the owner of Rush Creek Golf Course,where he was instrumental in attracting last weekend's LPGAtournament.

Duncan's Cargill career began with cleaning generators as ayouth. From the mid-'50s to the mid-'60s, he oversaw Europeantrading for eight years, based in Geneva, then came back toMinnesota to run Waycrosse, formerly Cargill Securities Co., whichhad been set up as a trust to protect the company's assets. In the1970s, he was instrumental in steering the company toward its steelinterests. From 1966 through 1997 he served on the board ofdirectors, and he is now a director emeritus.

Duncan spends his time playing golf, raising orchids, putteringwith his ham radio in the basement and getting his captain's licenseso he can pilot his yacht in Florida, where he also maintains ahome. In September 1996, he married Nivin Snyder, 55, also ofWayzata.

While his two-story house could be called typical of the uppermiddle class, it does not look like the castle a man of his wealthmight erect. And with characteristic MacMillan frugality, hissartorial style is more "fall into The Gap" than ascots and drivinggloves.

"Nivin tells me I dress like a farmer," he said, giving hiswife a poke in the arm. "I tell her, well, that's really what Iam."

MacMillan 's philanthropic contributions have been funneledprimarily into causes and institutions about which he is passionate- medicine and his alma mater, most notably. He and his late wifeSarah (Sally) MacMillan donated $1.1 million to the MinneapolisChildren's Medical Center in 1993 to build its pediatricintensive-care unit, and over the years Duncan has donated nearly$20 million to Brown University, where he has funded a sciencecenter and gym facilities and endowed a number of chairs in liberalarts.

MacMillan calls his relationship with Brown "one of the mostimportant commitments of my life.""He has 3 B's and a C for his midterm, which in the history of ourbranch of the MacMillan family is something unparalleled."

Sally, who died of cancer three years ago at the age of 63, wasan avid gardener. In her memory, Duncan has contributed a newterrace being built at the University of Minnesota Arboretum inChanhassen.

But considering their prominence in the Minnesota businessarena, the family has a much lower profile than the likes of theDaytons and the Pillsburys.

In Duncan MacMillan 's view, his family's downplayed communitypresence parallels that of Cargill's familiarity to the generalpublic.

"We don't sell products that go into people's mouths or ontheir bodies," he said. "We sell to the people who sell them."

Life with father

The Cargill/MacMillan union formally began when John HughMacMillan Sr. and Edna Cargill were married in 1895 in La Crosse,Wis., where both families were then based. Control of the businessshifted from the Cargill to the MacMillan side of the family in1907, a few years after the move to Minneapolis and the death ofpatriarch Will Cargill.

John Jr., Duncan's father, was born in 1895. Duncanremembers his father as an aggressive personality who cut his ownhair because he didn't like to be touched and was so competitivethat he would profess to having excelled at sports that didn't existin his youth, such as water-skiing. An early proponent of healthfuleating, he held that a radical 1950s diet of rice and fruit juicesaved his life, and eschewed salt long before it was fashionable.

MacMillan described his parents' style of child-rearing as"Victorian. There was a distance between us and them. In today'sworld there's more of an exchange in the relationship. I can't sayone is better than the other - it's just different."

The property his grandfather bought in what is now Orono wassplit among the MacMillan families. The Whitney boys, includingWheelock Jr., lived across the street, and were practically familyas well. The boys roamed in packs, going to breakfast clad in theirhockey clothes in the winter and playing baseball, kick-the-can andhide-and-seek in the woods in the summer.

back-yard circus and had a real flaming hoop rigged up that we wereshooting through on our bicycles. Grandpa came out and put a stopto that."

One of the craziest stunts MacMillan cooked up as a teenagerwas playing Jacques Cousteau with his best friend David Bell, whosefamily founded General Mills. According to Duncan, the two put onsome diving suits, the "heavy old kind that if you fell over in themyou couldn't get up," and walked themselves across the bottom ofLake Minnetonka, breathing through rubber tubes attached to ahomemade air tank set up on an unmanned boat above them.

Bell, a Marine pilot during the Korean War, died in 1955 whenhis plane crashed in fog over the Sea of Japan.

Keeping focused

MacMillan said the most important lessons he learned from hisfather were "discipline and honesty. And sacrifice - thecorporation came first. From my mother, it was social skills - anarea in which I have a lot of talent."

To outsiders, however, it seems that the most important lessonthat all MacMillans have learned is to keep their affairs, bothpersonal and professional, to themselves. While past and presentgenerations of the family have had their share of the kind ofproblems no family wants to broadcast (such as drug and alcoholaddiction), their obsession with privacy is all-encompassing.

"The grain-business philosophy of being close-mouthed goes backto the ancient Greeks," Duncan said. "When a fellow going into porthad more cargo than he sold and other people found out about it, themarket would collapse. So they tended to be that way about theirwhole lives, not just inventories and stocks."

"My grandfather hated getting his name in the paper. Timemagazine once printed an article criticizing the company, and hisway of commenting was to call up and cancel his subscription. . . .We don't talk about the family, period."

"In order to survive the tremendous upheaval of booms andbusts, you have to be patient. A farmer will never admit to having agood year or a bad year, no matter how profitable or grim it gets;he'll always say things are solid. No matter who asks, he's notgoing to talk about it. I guess we inherited that."

Duncan's book might be the most personal history of the familyto which the public will ever have access. And his role as familyhistorian might be what he himself is most remembered for.