Most Americans already know that Canada has polar bears, Eskimos, hockey stars, Mounties, and clean and handsome cities - but probe beyond that travel-poster surface and our ignorance of Canada becomes glaringly apparent.

If "The Group of Seven," the painting exhibition which opens today at the Phillips Collection is any indication, we are about to be instructed and surprised.

It is a lovely exhibition of paintings virtually unknown here. One can almost feel the crispness of the air and the shifting of the seasons in these freely brushed and brightly colored paeans to the beauties of the wilderness of Canada. There are 44 pictures on display. The best of them were painted more than half a century ago.

The "Group of Seven" exhibition is the first event in "20th-Century Canadian Culture: A Symposium," an 11-week series of exhibits, film showings, lectures and discussions on such subjects as "Is There a Distinctive Canadian Poetry?," "Is There a Distinctive Canadian Prose?" and "Living in the Shadow - the Americanization of Canadian Culture."

The Association for Canadian Studies in the United States, a private, nonprofit educational organization, is sponsoring the symposium. A $50,624 grant from the National Endowment for the Humanities will pay most of the bills. Symposium events, free and open to the public, will be held at the Phillips, the Hirshhorn Museum and Sculpture Garden and at the John F. Kennedy Center for the Performing Arts.

The pictures at the Phillips seemed to some outrageous when they were new, especially in contrast with meticulously detailed academic landscapes or with the yellowish cow-and-day-stack Barbizon nocturnes then so much in vogue. In Canada today, the "Group of Seven" painters are seen as pioneers of modernism, but it is not their modernism that moves us now. Rather it is their passion, the enthusiasm with which they painted the wilderness they loved.

There are more than seven painters in the "Group of Seven" (nine are represented in the Phillips show), but "Group of Seven" is the title under which they first showed together in Toronto in 1920. Even at that date, their most innovative colleague, the man they called their "guide," was already three years dead.

His name was Tom Thomson. He died under mysterious circumstances, perhaps drowned, some say murdered, while canoeing in Algonquin Park in 1917.

A kind of Canadian Thoreau, who shunned his country's cities in preference for her wilderness. Thomson spent his last years as a guide and forest ranger. He camped, hiked and canoed, and everywhere he painted. He painted summer skies and autumn skies (in Canada one sees the difference), lakeshores seen by moonlight, the foliage of trees. Like many of his colleagues in the "Group of Seven," he quickly painted what he saw on page-size wooden panels. Even when most roughly sketched, his victures have a kind of outdoors grandeur. Though tiny they seem big.

The impastoed post-impressionism of van Gogh and Vuillard was no longer new when Thomson did these pictures.

The thick paint and bright colors of the post-impressionists were no longer new the "Group of Seven" gathered. The triumph of abstraction, in Canada at least, was still yet to come. In the pictures on display here those developments are linked.

The painters represented here - Thomson (1877-1917), Frank Carmichael (1890-1945), A.J. Casson (1898-), Lawren Harris (1885-1970), A.Y. Jackson (1882-1974), Frank Johnston (1888-1149), Arthur Lismer (1885-1969), J.E.H. MacDonald (1873-1932), and F.H. Varley (1881-1969) - were free in their attack. They summarized the things they saw, the autumn leaves, the moving clouds, the white water of rapids, with gobs of goeey paint. But the colors they selected are the colors that they say.

It is their colors that are timeless. It is a memory of wilderness, as it looked then, as it looks now, that one carries from this show.

Duncan Phillips, the founder of the Phillips, would have loved these pictures. They are intimate, they're colorful, they pay homage to the natural, as do so many of the works he bought (by O'Keefe, Marin, Birchfield, an Rockwell Kent) on display nearby. Phillips bought the works he loved, then gave them to the public. So did Robert and Signe McMichael, the Canadian collectors, from whose home-museum in Kleinburg, Ontario, come all the light-filled landscapes in the Phillips show. It closes Feb. 20.