Art to sit on, art to hold a coffee cup, art to contain other treasures -- all are growing more popular by the day.

The price of antique furniture, the work of American wood craftsmen of the past, has gone sky high and rivals the paintings of the period -- a federal period desk for $5,000, a mass-made turn-of-the-century chair for $6,000.

There are great advantages in collecting art objects of wood. Wood is sturdy, long-lasting, not fragile; there is no danger in putting a wood art object to use.

Wood is a desirable medium to the artist because of its infinite variety and creative possibilities. The immense number of varieties of wood can be carved, bent, laminated, incised or ornamented in a myriad of forms.

And in a day when space, like money, is limited, wood furniture is not only there to look beautiful and appreciate in value, but also to use.

In recognition of that interest, Washington and Alexandria art galleries this month are showing the work of a few of the most important American woodmasters: Wendell Castle at Fendrick Gallery and Robert Trotman at Seraph, both in Georgetown; and George Nakashima at Full Circle in Alexandria. Always on view at Pond Gallery, in Alexandria, is Peter Danko, a local artist-craftsman who is becoming nationally known with his innovative bentwood designs. Joan Mondale -- at the vice president's residence -- has given important recognition to works by all four, as well as other wood artists.

Nakashima of Pennsylvania, one of the old masters of art woodworking, currently making the furniture for the International Paper Corporation's presidential suite in New York. A book on his life will soon be published by Kodansha Press. Trotman of North Carolina also has a piece in Buckingham Palace. Castle of New York has work in the Metropolitan, the Boston and the Philadephia art museums.

Here are some prices of the objects on view today through the end of the month. At Seraph: Trotman's face boxes (similar to one in the vice president's residence) range in price from $225 to $350; a set of two "atomic" stools, $400; "atomic" chair (maple, walnut and mahogany), $1,100. At Full Circle: Nakashima's bench, $1,600; rocking chair, $545; other pieces priced from $110 to $2,400.

At Fendrick: Castle's winged desk and chark, $12,600; single chairs, $1,450; Garnett chair and writing arm, $2,750; cherry chopping table, $3,950; cherry and mahogany doors with ribbons of glass, $5,900 to $6,900; conference table with eight chairs, $22,000; ebonized oak chair, $1,750. At Pond Gallery: Danko's rocker, $900 in oak, $1,100 in walnut; the footstool, $225 in oak or walnut; the Clyde's chair (designed for Clyde's restaurant), $350 in aok or walnut; glass and wood tables, $850.