Worthington Whittredge (1820-1910) was the Zelig of 19th-century American art. He was not a mighty master. He wasn't even close. But he possessed one curious virtue. He was eerily adaptable. Whittredge keeps showing up when you least expect him, a step or two behind the best landscape painters of his day.

Certain of his betters -- Frederic Church and Sanford Gifford, Albert Bierstadt and George Inness -- stand like peaks above the clouds. If you keep peering at those pinnacles, you're likely to miss Whittredge. But he's not that far away. He's always in the background, painting flexibly, and amiably, on the lower slopes.

The Whittredge one encounters in his touring retrospective -- it goes on view today at the Corcoran Gallery of Art -- seems not one man, but many. There is no single Whittredge style. He tried out half a dozen. His personality keeps shifting. On one wall he appears to be a typical Victorian, painting soppy genre scenes of old folks on the porch, or ladies in the parlor. Sometimes he paints seascapes, sometimes he paints Indians, sometimes he paints still lifes of apples on the bough. The Corcoran's exhibit is misleadingly subtitled "Hudson River Artist," for while Whittredge liked to think himself a member of the Hudson River school, the label doesn't fit. He might as well be called a German academic, a luminist, a specialist in Roman views, a Newport seascape painter, Barbizon School landscapist, an explorer of the Great Plains or a sketcher of the Alps.

Whittredge was born on a small hard-scrabble grazing farm near Springfield, Ohio. He wrote, "My ardent love of nature which dominated my whole being from my earliest recollections is the only thing I can look to as finally leading me to the study of art." He worked his way up, literally. First he painted baseboards. Then he painted signs for shops in Cincinnati. Though that city had produced its share of gifted artists -- the sculptor Hiram Powers, Robert Duncanson, Frank Duveneck and John Twachtman -- it could not hold young Whittredge. Instead he chose to work in Dusseldorf and Paris, in Colorado, Mexico, Manhattan and New Jersey. Whittredge got around.

His best landscapes are pleasant. They are well and freely painted. He was pleasant too. Whittredge was, by all accounts, an engaging man, modest, cosmopolitan, good-humored and kind. It seems most everybody liked him. His many friends included Robert Schumann, the composer, Theodore Roosevelt's father, and Kit Carson, the legendary scout. Artists of all sorts found Whittredge good company. He traveled in Italy and Mexico with Bierstadt. He worked in Switzerland with William Stanley Hasseltine, and in Rome with Gifford. When Emanuel Leutze painted his great potboiler, "Washington Crossing the Delaware," he had his young friend, Whittredge, pose proudly as the general standing in the boat. Whittredge, in his heyday, was an art star in New York.

In the mid-1870s, his peers elected him president of the National Academy of Design. And he helped to found the Met.

And everywhere he lived, he somehow took on his surroundings. Whittredge all his life was peculiarly amenable. If his customers required a shop sign that read "Porkhouse," or a scene of a fine sunset above the wild forest, or views of Indians and their teepees, or a copy of a picture he had made before, Whittredge would oblige. In Dusseldorf, when young, he painted mighty German oaks, and fierce Teutonic warriors battling for castles. He painted the Matterhorn in Switzerland. In Italy his subjects were similarly predictable. He painted "The Cypresses in the Villa d'Este, Tivoli" in 1856, and, of course, ruined aqueducts, and Romulus and Remus being suckled by a wolf.

Compared to most of his American contemporaries, Whittredge was widely traveled and exceptionally well trained. He could conjure up the look of mossy rocks and babbling brooks and sunlight on the sea with admirable dexterity, but charming and appealing though his finest paintings are, they are rarely more than that.

Art historian Anthony F. Janson, who organized this show and wrote the useful monograph that serves it as a catalogue, has studied Whittredge for 16 years, but even he would not describe Whittredge as a master. He writes, "I have tried to resist the temptation felt by every author to justify his studies by exaggerating the importance of his subject... . Whittredge, it must be said, was not one of the pioneering spirits who defined the Hudson River school. He does not rank in importance with the likes of Thomas Cole and Asher B. Durand in the preceding generation, or Frederic Church, Albert Bierstadt, John Kensett, and Sanford Gifford among his own... . He did not possess the temperament needed for such a role. Nor did he have the requisite talent."

What he had was flexibility. When, in 1859, he returned to the United States after a decade in Europe, the Hudson River style was already much in vogue. European landscapes -- views of German oaks and battlements, alpine scenery and aqueducts -- had fallen out of fashion. America was seeking art that looked American. Whittredge understood that. And so he set to work.

"It was impossible to shut out from my eyes the works of the great landscape painters which I had so recently seen in Europe," he wrote, "while I knew well enough that if I was to succeed I must produce something new which might claim to be inspired by home surroundings. I was in despair. Sure, however, that if I turned to nature I should find a friend, I seized my sketch box and went to the first available outdoor place I could find. I hid myself for months in the Catskills. But how different was the scene before me from anything I had been looking at for many years! The forest was a mass of decaying logs and tangled brushwood, no peasants to pick up every vestige of fallen sticks to burn in their miserable huts, nothing but the primitive woods with their solemn silence reigning everywhere."

That solemn woodland views by older Hudson River artists were already selling like hot cakes must have helped him make the switch. And when, a few years later, he detected a demand for Ye Olde American genre scenes of gentlemen and ladies in 18th-century clothes, Whittredge moved at once. When, just after the Civil War, painters started hymning the drama of the Wild West, Whittredge joined the throng. In June 1866, he set out on the old Oregon Train with Gen. John Pope. Their expedition traveled -- with tents and covered wagons -- from Ft. Leavenworth to the Rockies, and then south to Santa Fe. The little scenes he painted while on that rough journey are among the mildest, least hokey, most compelling, pictures in his show.

Whittredge was thriving now. His landscapes of the West and of the Hudson River Valley were everywhere applauded, and selling nicely too. (In 1875, William Wilson Corcoran, the founder of the gallery, bought "Trout Brook in the Catskills" directly from the artist while its paints were still wet.) But fashions have a way of shifting of a sudden. The vogue for Whittredge's sort of landscapes -- his intimate, subtly romantic, and meticulously composed visions of America -- ended in the '80s just about as quickly as it had begun. Excessive details were out, so were sunset histrionics. A new sort of landscape painting based on European models, a new and brownish style rich with grazing cows and pastorale, light-diffusing mists and out-of-focus trees, was suddenly in fashion. The Barbizon School manner was everywhere triumphant. Whittredge's style changed again.

It says much for his honesty that he never hid the major debts he owed to other painters. "It has been one of the greatest pleasures of my life to study their work," he wrote, "not so much for any dexterity that might be displayed as to ascertain what they were thinking of that was new and original." His own work was neither very new nor very original. It grew weaker as he aged. Whittredge's canvases, in the 1870s, had often fetched as much as $1,200. By 1900 they were selling for $40 each. His last picture is dated 1903. He was three months shy of 90 when he died in 1910.

"Worthington Whittredge: Hudson River Artist" is a sort of half-baked exhibition. What points it strives to make are seldom made with clarity. It includes some moving, handsome works -- "Landscape Near Minden" (1855), "Twilight on the Shawangunk Mountains" (1865), and "Second Beach, Newport" (1878-80) are among the most impressive -- but even these fine pictures cannot quite dispel the mood of wavering and shifting that dominates the galleries. Perhaps the fault is Janson's. One cannot help suspecting that had his exhibition been more judiciously selected, or more pointedly installed, it might have taught one volumes about American landscape styles in the last half of the 19th century. Perhaps the fault is Whittredge's. He had subtlety and charm and considerable skill, but his varied landscape paintings rarely move one deeply. Neither does his show. It was organized by the John and Mable Ringling Museum of Art. It will remain at the Corcoran through Nov. 4.