Fifty-six ornaments, 18 of them fiberglass reproductions, from the Sullivan Architectural Ornament Collection at Southern Illinois University at Edwardsville, are on display through July 6 at the Octagon, 1799 New York Ave. NW.

The show, "Unison With Nature," includes pediments, ceiling screens, door panels, elevator grilles and windows shaped from terra cotta, wood, iron or copper from 1881 to 1919. Scrolls, lightning bolts, leaves, stars, circles, all intertwined, seem to almost exhaust the possibilities of ornamentation. Of particular note are the doorknobs and plates and the oak grilles from the Riverside, Ill., residence of Henry Babson, and the cast iron and bronze elevator grille from Chicago's old Schlesinger and Mayer department store, now the Carson, Pirie, Scott building.

Unfortunately, the fiberglass reproductions look like wedding cake decorations that have been sat upon. Most of them are grouped -- perhaps it would have been better to quarantine them -- in a section of one gallery. Avert your eyes when you come to them.

An accompanying catalogue gives a useful summary of Louis Henri Sullivan's life and work. Sullivan fancied himself a writer as well as an architect (his copy of Walt Whitman's "Leaves of Grass" in the exhibit shows how he dared even to rewrite the poet) and his writings on architecture are still essential reading for architects: "Autobiography of an Idea," "Kindergarten Chats" and "A System of Architectural Ornament." The exuberant flowering of architectural ornamentation came in the last quarter of the 19th century in Chicago when Sullivan founded the Chicago School. He later became liebermeister to Frank Lloyd Wright and his Prairie School.

Along with the work of New York's Louis Tiffany and California's Greene and Greene, Sullivan's work constitutes the most important American expression of art nouveau, the seed of the modern movement. Though like most architects he scorned art nouveau as "mere decoration," claiming instead that "form ever follows function," he looked to nature for design forms like the nouveau artists did. The art nouveau style of limpid ladies and virulent vegetation entangled design on the European continent from 1890 until it was killed in World War I. Art nouveau's worship of unpruned nature spread over everything -- clothes, architecture, furnishings, books, jewelry and stage design.

Sullivan first encountered art nouveau when he studied at the Ecole des Beaux Arts in Paris in 1875. His studies also gave him an appreciation of geometry. He left Paris after a year, in search of a less academic, more American and more personal style, as he wrote: "This Great School, in its perfect flower of technique, lacked the profound animus of a primal inspiration . . . "

Back in Chicago, he remained faithful to the romantic movement, even in the face of the conquering Roman and Greek neoclassic movement spearheaded by the 1893 Columbian Exposition. At this world's fair, his Transportation Building, in the Byzantine mode, was the only holdout against the "White City" of neoclassicism. (In Washington, Thomas Jefferson and architects William Thornton and Benjamin Latrobe were early advocates of the "glory that was Greece and the grandeur that was Rome.")

Sullivan became the designing partner in 1881 with Dankmar Adler, an engineer, and until the partnership ended in 1895, five years before Adler died, the two were responsible for 120 buildings, from houses to an exposition building. Today they are best known for Chicago's Auditorium, old Stock Exchange and Columbian Exposition Transportation Building and especially their work in developing the skyscraper, notably with the Wainwright Building in St. Louis.

The catalogue's authors, Linda L. Chapman, Joyce Jackson and David C. Huntley, credit the Sullivan-Adler achievements in the skyscraper to their "vision and genius and their ability to adapt several inventions of the 19th century to the inherent problems of the skyscraper": the electrically powered elevator and Bessemer process steel, which allowed them to build "a light masonry skin stretched over an internal steel skeleton," as the authors put it.

The arts and crafts revival, which encouraged handwork in both furnishings and architecture, was helped in Chicago by the turn-of-the-century influx of European craftsmen. Kristian Schneider, a German sculptor who settled in Chicago, executed the ornamental designs of Sullivan and later Frank Lloyd Wright and George Grant Elmslie. Both of these architects came to work with Sullivan and were profoundly influenced by him.

In the early 1960s, Southern Illinois University began its collection of architectural ornamentation, always only a step away from the wrecking ball. Richard Nickel, the photographer who recorded and rescued the ornaments for 20 years, died trying to save an ornament in the old Chicago Stock Exchange. The Octagon exhibit shows why he was willing to risk his life.