Though she tried to hide her celebrity status by using her maiden name, the diplomats who have been flocking to the Osuna Gallery, 2121 P St. NW, to see (and buy) the sculpture of Emilie Benes obviously were well aware that in private life, the artist is Mrs. Zbigniew Brzezinski.

She had not shown before in Washington, lest her work be judged and puchased for extra-artistic reasons. She need not have worried; her work stands firmly on its own.

There is, in looking at the sculpture of Benes, the magical feeling of being inside a tree, of exploring the seductive space within the tree as it reaches deep into the ground. It is, of course, a space that does not really exist-except for the occasiional animal who lives in its hollow.

It is through exploration of the surfaces of various trees that Benes has been able to give us access to the imaginary world within. Walking through the woods wherever she happens to be (she lives in McLean, Va.) she takes rubber molds of live tree bark that interests her, and later casts it in clear acrylic resin.

What results is a see-through reproduction of the tree-trunk segment, which has been subtly tinted. Cut away to a smooth surface at the front, the texture works from behind, catching and transforming the light, making it seem that one is inside the tree looking out.

Meanwhile, the works glow and shimmer infinite textural variations afforded by the bark itself, from the fine-grained, twisting "Englewood Maple" to the horizontal striations of the evocative "Swinger Mill Ancient Beech." Only one forked tree trunk and a long, curved piece fail to please at all.

The danger in working in this inherently elegant medium, and with such sure-fire subject matter, is that the results inevitably teeter on the brink of becoming decorative objects, and on occasion the sculpture here slips into that category. A few pieces sparkle and glisten but they are merely pleasing, not profound. One very large piece, deeply tinted green, has become far too lavish and elegant, too much the manufactured "beautiful object."

Benes avoids this pitfall most of the time, however, and at the other end of the spectrum are two pieces-"Graffiti Beech, Chain Bridge," and "Park Graffiti Tree"-that transcend everything else in the show. In these works, impressoins taken from nature have been transformed into iconic sculpture wherein mere scratchings become timeless hieroglyphs, exuding all the mystery of ancient cave drawings. For a first major solo this is, indeed, a commanding and beautiful show. It continues through May 12.

A small but provocative exhibition of "German War Art, 1939-1945," has just opened at the Fenwick Library of George Mason University in Fairfax, Va. No doubt it will attract more than its share of attention, for it includes four watercolors attributed to Adolf Hitler-an early piece done in Vienna, one from Munich, and two painted during World War I on the Western Front.

All are innocuous scenes in the contemporary realist vernacular. The draftsmanship is stiff but not that bad, and wonders why he was not admitted to the Vienna Academy of Fine Arts in 1907 when he applied.

These four drawings were, in fact, added to a traveling exhibition organized by the Army Center of Military History, which is custodian of some 9,000 paintings seized by the U.S. Army as propaganda art at the close of World War II, and stored in this country ever since. The shows usually take place at military installation. This is the first nonmilitary showing in the area.

The exhibition will continue through May 1, and a fine small catalogue giving historical context has been prepared by German History professor Marion F. Deshmukh. Call 323-2393 for Gallery hours.

Scott Burton's sculptural furniture, now at Protetch-McIntosh, 2151 P St. N W, grew out of stage sets he developed for his early '70s performance pieces, called "Behavious Tableaux." At first these small tables and chairs were merely props. During the past few years, however, Burton has abandoned performance to concentrate on furniture, working toward developing a genre that hovers between "object" and art, between furniture and conceptual sculpture.

Instead of playing the role of artist decorator, Burton actually uses the furniture as subject matter, and through it attempts to express ideas about art itself, particularly about various art-historical styles and their characteristics, which he sometimes seems to parody. It is an "insider's" kind of art.

A very minimal table and chair made of drab, bent metal, for example, looks like well-designed, "form-follows-function"-type furniture until an attempt is made to pull the absurdly heavy chair to the table. It will not budge. We are reminded that functionalism is something we have come to take for granted as part of the modern stylistic tradition.*tLikewise, a cube of galvanized steel, the very essence of minimalist sculpture is here outrageously embellished with checkerboards of irridescent mother-of-pearl to make a small table.

Burton, now 39, grew up in Washington, studied at the Corcoran School as a child, and at Western Hight School with color painter Leon Berkowitz before heading for New York, where he now lives. He was included in a recent Whitney Biennial, and in the Guggenheim Museum's recent "Young American Artist" exhibition. His show closes today.

Upstairs at Protetch-McIntoch, Corcoran instructor Benita Berman is having her first solo show of paintings and large graphite drawings, all based on a highly personal, instinctive minimal imagery. The works usually begin with a tiny object-a piano, a cup, a shirt-which is then surrounded by a flattened, schematized space that seems to carry within it a reinforcing mood.

At their best, thses are tender and evocative works that promise much for the future.

Touchstone Gallery, a cooperative at 2130 P St. NW., is showing the works of two members, Bea Eiges and Richard Stamm. As in earlier shows Eiges continues to carve well-crafted, nicely composed abstract forms in marble, seeking variation in stones of different color and texture, such as one work in purplish Lapidolite and smooth black basalt. One piece in basalt, called "Vision," is particularly striking, and has a welcome air of mystery.

The versatile Richard Stamm is showing a series of highly sensuous graphite drawings of seashells seen close up. Some of these border on the erotic. He also has created an amusing group of ceramic trompe-l'oeil bathroom towels that would be more satisfying if they really fooled the eye a bit more than they do. Through May 5. CAPTION: Picture, Emilie Benes with one of her sculptures-The Washington Post