Some very famous artists -- including Robert Rauschenberg -- began their careers as window trimmers for Fifth Avenue department stores. But James Linton Sain was dressing windows for Leggett's department store in Lynchburg, Va., when Ted Cooper of Georgetown's Adams Davidson Galleries found him a year or so ago. Now Sain has turned in his staple gun and fake snow for a fine brush, and Adams Davidson is giving him his first show.

If Sain's art is as different from Rauschenberg's as Lynchburg is from New York, both are worth knowing about. Once an abstract painter and theatrical costume designer, Sain now makes botanical watercolors of wildflowers, fruits and vegetables, all bits of flora that he picks and then paints in his Blue Ridge Mountains studio. His images are sufficiently accurate to have attracted the attention of the National Arboretum (where they were shown last month) and the American Horticultural Society (which cosponsored this show). But their rhythmic outlines, bold compositions and metaphorical overtones also make them highly satisfying works of art. Tiny pencil drawings of plant details, placed in the corners, balance the page and add a nice signature touch.

Precise as they are, none of Sain's weeds or flowers or eggplants or Bartlett pears is manicured before its "portrait" is taken. Rather, Sain prefers to leave the scars as he traces out the life process of a particular plant. A stalk of "Trumpet Creeper" typically bears not only a bud, a dead bud and a bloom, but next year's seedpod; blackberries are shown in every stage of color development; in a strikingly handsome watercolor of Jimson weed, the leaves have obviously not escaped the insects. "My pictures are metaphors of the life stages of man . . . the span of life," says the artist. "I just happen to use wildflowers as a subject to illustrate this idea." Not all of these watercolors are as beautiful as the delicate pink fumewort and the lacy southern harebell, but all command respect, and suggest that Sain was wise to abandon window trimming for art. His work can be seen through Dec. 1 at 3233 P St. NW. Gallery hours are Tuesdays through Fridays, 10 to 5, Saturdays, noon to 6. American Impressionism Show

Just a few doors away, at 3241 P St. NW, Taggart, Jorgensen & Putman is showing "American Impressionism, 1880-1930," a group of 30 landscapes and portraits by two generations of American painters who worked chiefly in New Hope, Pa., Boston and elsewhere in New England. As often happens in commercial shows of this sort, in which all the works are for sale, those by big-name artists -- here represented by Childe Hassam, Edward Potthast, Winslow Homer and John Singer Sargent -- tend not to be first-rate.

The most interesting paintings are by lesser-knowns, like Daniel Garber of New Hope, who is represented by a panoramic, tree-filled view of "Stockton, N.J." seen across the river. In the foreground, figures play croquet on a broad, shaded lawn as the entire scene is bathed in an eerie glow. Light plays a major role in all of these works, though many stray far from classic French Impressionism. William McGregor Paxton of Boston, another star of this show, has made the riveting pastel "Portrait of a Young Woman" that looks more like something by Balthus, the contemporary realist, than any Impressionist one can think of.

Brief but informative labels accompany the paintings, and they are especially helpful. The show will continue through Nov. 23. Hours are Mondays through Saturdays, 10:30 to 5. WPA Auction

Washington Project for the Arts (WPA) will hold its Sixth Annual Art Auction -- always a bargain-filled affair -- next Saturday at the Departmental Auditorium, 12th Street and Constitution Avenue NW. Works by more than 160 area artists, well known and unheralded, have been selected by a six-person committee of artists and collectors on the WPA board of directors. The result: the closest thing to a broad survey of good, current Washington art that you're likely to see.

Among the better known artist-participants: Catherine Batza, Leon Berkowitz, Benita Berman, Raya Bodnarchuk, Emilie Brzezinski, Peter Charles, William Christenberry, Jerry Clapsaddle, Suzanne Codi, Rebecca Davenport, Claudia DeMonte, Kevin MacDonald, Ed McGowin, Jody Mussoff, Tom Nakashima and on down through the alphabet to Yuriko Yamaguchi. The goal of the auction is to help WPA raise funds to match its $84,000 challenge grant from the National Endowment for the Arts. But the artists also will benefit: Fifty percent of all proceeds from sales will go to them. Last year, the auction generated $100,000, of which more than $40,000 went to Washington artists.

To give young collectors some inspiration -- and potential buyers a chance to examine the 200 paintings, sculpture, prints, photographs and other works of art to be auctioned off -- a pre-auction exhibition is now on view at WPA, 400 Seventh St. NW, and can be seen today and next week, Tuesday through Saturday, from 11 to 7. Several smaller works are part of a silent auction, for which bids are being taken until the day before the live auction.

The exhibition is free, but tickets to the benefit auction are $25 (which includes a cocktail reception) or $75 (which includes cocktails, a buffet dinner and reserved seats for the auction). Call 347-4813 for reservations. Sandro Chia at the Hirshhorn

Sandro Chia, the best known of the Italian painters included in the Hirshhorn's current examination of "A New Romanticism: Sixteen Artists From Italy," will engage in a dialogue with exhibition curator Howard Fox at the Hirshhorn at 8 p.m. Wednesday. The Smithsonian Associates-sponsored event has a $10 admission fee.