There'll be no tricks but lots of treats -- and bargains -- in the art galleries around Dupont Circle today. To benefit the needy Phillips Collection, nine neighboring galleries have put up special selections from current stock and will donate 20 percent of today's sales to the museum. In addition to discounted prices on many works, buyers can also deduct 20 percent of their purchases as a tax-free contribution to the Phillips. Washington printmaker Scip Barnhard has also made a striking commemorative lithograph (edition of 60) depicting Duncan Phillips standing in front of his museum, to be sold today for $100 (and $150 thereafter), with all proceeds going to the Phillips.

The benefit and self-guided tour of the galleries takes place from noon to 6 today, and will culminate in a cocktail reception for all purchasers and dealers at the Phillips at 6:30. Tour maps can be picked up at Gallery K, Hom, Touchstone, Jane Haslem, Barbara Fiedler, Baumgartner, Fondo del Sol, Addison/Ripley and Middendorf/Lane. The highlights include the following:

* Barbara Fiedler Gallery, 1621 21st St. NW, has a rare and wonderful show of work by Karl Knaths (1891-1971), a Wisconsin-born artist who spent most of his life in Provincetown, Mass., and who had a productive association with the Phillips Collection. In 1926, Duncan Phillips bought the first painting Knaths ever sold -- the first of 60 he ultimately acquired. Between 1938 and 1950, Knaths also spent three months each year at the Phillips as artist-in-residence.

The Fiedler show consists of drawings, watercolors and monotypes, most of them related to the paintings in the Phillips -- lyrical, semi-abstract scenes of the Cape Cod environment, including dunes, moors, the sea and the artist's beloved animals. Those who know the collection well will have the added pleasure of seeing how this early modernist worked out his basic themes and did variations upon them. "Geraniums in Night Window," for example, is represented by a straightforward pencil drawing, a woodcut, a watercolor and a spare, highly abstract color pencil study, which actually preceded the Phillips painting by one year. There are several studies for his barroom series and for "Frightened Deer in Moonlight." Among the most beautiful works are the monotypes and a wholly abstract oil on paper entitled "Stripes."

Although Knaths is included in museum collections all over the country, he has never had a major retrospective, which may account for the reasonable prices. The exhibition continues through Nov. 17.

The works by Knaths are not part of the Phillips benefit, but among those that are in the specially priced benefit show are a marvelous watercolor by Knath's friend and colleague Oliver Chaffee (appropriately depicting a Halloween witch), a Motherwell drawing and prints by Larry Rivers, David Hockney, Alex Katz and Jacob Kainen. The gallery is open Tuesdays through Saturdays, 11 to 5.

* At Hom Gallery, 2103 O St. NW, Leonard Cave, who has long had an underground reputation in Washington, here establishes himself as one of the best wood sculptors now at work -- anywhere.

Cave works with giant chunks of raw wood -- oak, cherry, walnut, poplar -- all coarsely cut from stripped, weathered tree trunks and then gouged and grooved with everything from a chain saw to a fine chisel. The chunks are bolted together into bold, soaring compositions, such as "Kensington Arch," which also manages to convey the artist's more subtle passion for his material through delicate juxtaposition of color and texture.

This show, not to be missed, continues through Nov. 16, and is open Tuesdays through Saturdays, 11 to 5.

For the benefit sale, Hom is showing drawings by French painter-critic Andre Lhote (1885-1962), lithographs by Matisse and Chagall, and turn-of-the-century French and Belgian art nouveau posters -- his usual high-quality fare.

* Jane Haslem, 2121 P St., has turned over her entire space to the benefit show, which includes everything from inexpensive posters to paintings by Billy Morrow Jackson and John Winslow. Of special interest are several American prints from the 1920s and '30s by John Sloan, Martin Lewis, Claire Leighton, John Costigan and others, and contemporary prints by David Itchkawich, Bruce McCombs and Hnizodvsky. This show is today only, from noon to 6.

* Gallery K, 2032 P St., has put some odds and ends together for the benefit sale, none of them less interesting than the current featured show, possibly the worst in the gallery's history. Perhaps taking their cue from the recent Timberlake fiasco at the Corcoran, Gallery K is featuring Virginia artist Durwood Dommisse, an impressionistic landscape painter who teeters dangerously close to producing pure calendar art, of which "Early Evening, Gurgle Creek" is the most crass and passionless example. There is one good painting, the moody "Lonesome Road," which suggests that Dommisse could do better if he could shake off the habits one suspects he learned in a Christmas card factory.

In the back room at Gallery K, there is a far better show of gouaches by newcomer Michael Murabito, 26, who makes small, cubistic abstractions of great sophistication. His collages, however, tend to be overworked. Both shows continue through Nov. 14. Gallery hours are Tuesdays through Saturdays, 11 to 6.