"Two Centuries of Black American Art," the large museum show that has been traveling the country, includes black art by Americans as well as art by black Americans. For most of our art history, as David C. Driskell acknowledges, the two things weren't the same.

Driskell, the University of Maryland professor who organized the show, begins his catalog by questioning "the tradition of classifying people and their culture according to race. The black artist," he continues, "has neither wanted nor accepted this critical isolation" - yet just such isolation is encouraged by his show. Driskell sees the irony. He knows his exhibition documents "a body of work that should never have been set apart as a separate entity."

From 1750 until the Negro Renaissance of the 1920s, for reasons not mysterious, most artists who were black painted in the "mainstream" for an audience that was white.

Baltimore limner Joshua Johnston (1765-1830), who did portraits of the gentry; bird painter John James Audubon (1785-1851), whose father was a wealthy Frenchman and whose mother was mulatto; landscape painter Robert S. Duncanson (1821-1872); Barbizon painter Edward Michael Bannister (1828-1901), and neo-classical sculptor Edmonia Lewis (1843-1900), rarely in their art celebrate their blackness.

Not until the 1920s, with the raising of black consciousness, did that situation change.

"I do not care a damn for any art that is not used as propaganda," wrote W. E. B. DuBois in 1926. He believed, as Alain Locke believed, that the heritage of Africa could prompt "the reexpression of a half-submerged race soul." African art, wrote Locke, "presents to the Negro artist in the New World a challenge to recapture this heritage of creative originality, and to carry it to distinctive new achievement in a vital, new, and racially expressive art."

Much art made since then by gifted black Americans - Romare Bearden, Aaron Douglas, Horace Pippis, Charles White, Jacob Lawrence, Elizabeth Catlett, Hughie Lee-Smith, Alma Thomas, William H. Johnson, all of whom are represented in Driskell's exhibition - has fulfilled Locke's prophecy.

In the spirit, pride and attitudes it seems both old and new. The heritage of Africa, though concealed in those years when black artists swam the mainstream, has been apparent in this country since the days of slavery. In early Southern crafts and carvings, in some plantation architecture, as well as in much recent art made by black Americans, Driskell sees what he describes as "survival or retention forms."

He sees it in the colors, in the rhythms and the patterning, and he sees it on the street. "Africans communicate in the most complex ways through the things they wear, head-dresses, weavings, jewelry, staffs. In America, the absence of regalia has been partially made up by what is sometimes called 'loud dressing.' African craft styles and body arts similarly have given something to the hats and coiffures worn by American blacks."

Symbolic figures in the West - Caesar, Lincoln, Queen Elizabeth - are frequently evoked by portraits. In Africa, the evocation is often done by masks. Driskell agrees that many black painters in America avoid specific portraits, preferring, instead, to make mask-symbols out of faces.

His exhibition opened last year at the Los Angeles County Museum of Art, where 100,000 people saw it. It has since been seen in Dallas and Atlanta. It will not come to Washington, but on June 22 it will open at the Brooklyn Museum in New York.

Driskell, 46, is both painter and art historian. He was trained at Howard University, and while in Washington studied with color painters Morris Louis and Kenneth Noland. He came to Maryland this year from Nashville, where he served for 10 years as the chairman of the art department at Fisk University.

"One thing has bothered and confused people about the exhibition - the cut-off date," says Driskell. "Though it ends in 1950, I've included newer works by artists Alma Thomas, Romare Bearden, and some others, who were active at that time. It would have been a very different show had we represented artists of the younger generation, but the Los Angeles County Museum decided not to. They thought there ought to be a breather between the present and the past. Their decision was political, I'm sure of that."