If you think that recent painting has been blighted by the trivial, by marketing and hype, facetiousness and flash, you ought to pay a visit to the latest "Spectrum" exhibition at the Corcoran Gallery of Art. It's not a shining show -- it is in places somewhat clumsy -- but its seriousness is palpable. Washington's William Willis and New York's Clifford Ross are the painters represented. Their pictures do not look alike. But there is much they share.

They avoid bright, plastic colors. The hues that they prefer are those of leaves and bark, of clouds and earth and sky. They distrust the flip, the facile. There is patience and much labor in their often-somber pictures -- and an old familiar hunger, a yearning for transcendence.

Both once pledged allegiance to purely abstract painting. Willis, who now teaches at the Corcoran School of Art, used to make precise geometrical abstractions; Ross, who studied art at Yale, was once committed to color field painting. But like many other artists of the 1980s, both have since been reaching for something more substantial, for something that would counter the hollowness, the coldness, at pure abstraction's core.

Both Willis, who was born in 1943, and Ross, who's nine years younger, discovered their ways forward by looking toward the past. Willis turned to India, to the lingams and the mantras, the images and ancient texts of sacred Indian art. Ross bent his art toward landscape. Like Constable and Ryder, he began seeking the sublime in the shifting grandeur of sea and earth and sky.

Their paintings are not literal. When Willis paints a serpent he does not show its scales, and that fresh plant in the garden, with its mouth turned toward the sky, is as much a tulip as it is a tree. Ross' textured landscapes are similarly invented. His paintings are produced on Lower Broadway in Manhattan. The scenes of France and Wales that appear in his pictures come out of his mind.

Willis is much admired by artists in this city. Last year he was given a Pollock-Krasner Foundation grant. He was also among the recipients of the 1987 Awards in the Visual Arts. But in spite of such approvals, I'm afraid I find his paintings hard to take.

There is a heaviness about them that seems, at least to me, wholly antithetical to the rhythmic interweavings, the dancings and the delicacies of classical Indian art. His khakis, grays and earth tones often tend toward muddiness. His surfaces are rich. He frequently contrasts the shiny with the matte. And often one can see him overpaint an image time and time again until just its ghost remains.

But the symbols he presents do not always work (that green tree in the garden is a notable exception). The images that Willis eventually arrives at -- a black, down-pointing triangle, a thick five-headed serpent or a spiral that is either a seashell or a galaxy -- may be, for the painter, pregnant with much meaning, but they seem, to me, inert.

I find more seductive the sunsets and the cloudscapes, and the mustard-yellow meadows in Ross' textured paintings. His pictures aren't rectangular. Neither are they flat. He begins with a thick panel on which he fastens burlap, fabric he then covers with thick papier-ma~che'. The palpable physicality of that dense, encrusted surface nicely contrasts with his deep and airy landscapes.

This "Spectrum" show was organized by adjunct curator John Beardsley. It is one of three such exhibitions the Corcoran will offer in 1988. This year's series is partly funded by a $30,000 grant from the Philip Morris Cos. Inc., a firm that more than most is willing to support new, chance-taking art. The Ross and Willis show closes April 10.