The High Museum of Art in Atlanta will open "Alfred Stieglitz and His Circle: American Moderns From Atlanta Collections" and "John Marin's Watercolors: A Medium for Modernism" on Saturday.

The Stieglitz show will feature about 600 watercolors, prints, paintings and drawings that are part of the High's permanent collection or are on loan from Atlanta collectors. The pieces on display were created by Stieglitz and other artists who engaged with him during the course of five decades - from the early works of Max Weber to the mature expressions of John Marin and Marsden Hartley and finally, to the progressive photographic compositions of Paul Strand and Edward Steichen.

The exhibition will showcase how Stieglitz's impact extended well beyond his individual support of singular artists. His format of grouping and promoting new talents - photographers, painters and sculptors alike - created a loose-knit community whose shared purpose was to advance new approaches to artistic representation. His galleries served as avant-garde incubators in which new forms of art were presented, often for the first time in the United States.

Already an accomplished pioneering photographer by the time he opened his famous Gallery 291 in 1905, Stieglitz shifted focus around 1909 to primarily promoting and advancing modern art in America through shows and in his quarterly photographic journal "Camerawork." Stieglitz's earliest work supported an expansive group of artists who practiced a modernism reflective of European influences, such as continental Cubism and Expressionism as seen in the works of Arthur Carles, Oscar Bluemner, Abraham Walkowitz, Alfred Maurer, Weber, Marin and Hartley.

After World War I and with the closing of Gallery 291 in 1917, Stieglitz shifted toward a more exclusive group of artists, whom he featured in a series of new exhibition spaces - The Anderson Galleries, The Intimate Gallery and An American Place - modeled after Gallery 291's initial success.

The Marin exhibition, organized by the Art Institute of Chicago, was largely drawn from that museum's Stieglitz Collection given by modernist painter Georgia O'Keeffe in honor of her late husband. Marin was a central artist in Stieglitz's circle, and the two maintained a close working relationship and deep friendship for 40 years.

Both exhibitions continue through Sept. 11.

The High, 1280 Peachtree St. N.E. in midtown Atlanta, is open 10 a.m.- 5 p.m. Tuesday, Wednesday, Friday and Saturday; 10 a.m.-8 p.m. Thursday; and noon-5 p.m. Sunday. Admission is $18 adults, $15 seniors/students, $11 ages 6-17 and free for ages 5 and under. Call 404-733-4444.