Théodore Rousseau, "Study for The Forest in Winter at Sunset" (ca. 1846), oil over charcoal with white heightening on paper, mounted to canvas, 9 5/8 x 13 1/4 inches. Private collection (all images courtesy the Morgan Library & Museum)

Théodore Rousseau, “Study for The Forest in Winter at Sunset” (ca. 1846), oil over charcoal with white heightening on paper, mounted to canvas, 9 5/8 x 13 1/4 inches. Private collection (all images courtesy the Morgan Library & Museum)

Consider “Study for The Forest in Winter at Sunset,” a work in oil and charcoal on brown paper by Théodore Rousseau, the 19th-century French painter now under scrutiny at the Morgan Library & Museum. Although it was done between 1845 and 1850, it feels like something Anselm Kiefer might come up with for a 12-foot-wide canvas: a controlled chaos of bare, twisting tree limbs in slashes of paint as dark and smoldering as charred bitumen.

Rousseau’s study is just an inch or two larger than a piece of typing paper, but it captures the bleak, commanding presence of the Forest of Fontainebleau, where it was made. Its scraggly oaks emerge from the sepia-colored ground amid smears and stipples of charcoal, filling the sheet’s wide horizontal midsection with black, oily strokes. Blue-gray flecks of sky breaking through sulfuric clouds and isolated patches of pearlescent sunlight sink the paper’s burnished, autumnal glow into a dank, biting chill.

The image is blunt and raw, especially when compared with the limpid, fluidly brushed oil paintings that make up the opening section of the Morgan’s neatly compact exhibition, The Untamed Landscape: Théodore Rousseau and the Path to Barbizon. Like many works in the show — most of them exquisite and all of them on paper — Rousseau, in all probability, believed that this study would be seen by his eyes only. An absence of viewers’ expectations might account for the restiveness in his materials and imagery, which change like the weather from one sheet to the next. Working onsite and surrounded by his subject, the notion of a unified style would take a back seat to his spontaneous response to the environment — or so you would think.

In his review of the Paris Salon of 1846, Charles Baudelaire counted Rousseau among the exhibition’s “most celebrated absentees,” deploring the “setbacks and underhand plotting” that kept him out of the running, and his consequent status as “a man but little known to the multitude.”

Baudelaire writes that Rousseau’s talent “is as difficult to interpret […] in words as it is to interpret that of Delacroix,” but he does a splendid job nonetheless:

His painting breathes a great sigh of melancholy. He loves nature in her bluish moments—twilight effects—strange and moisture-laden sunsets—massive, breeze-haunted shades—great plays of light and shadow.

In a piece on the Salon of 1859 (which did include Rousseau’s work), Baudelaire goes a little deeper. Comparing him to Jean-Baptiste-Camille Corot, whose paintings were also in the salon, Baudelaire notes that Rousseau “is perpetually restless and throbbing with life—if Rousseau seems like a man who is tormented by several devils and does not know which one to heed, M. Corot, who is his absolute antithesis, has the devil too seldom within him.”

As evidenced by the fine selection on view at New York’s Metropolitan Museum of Art, Rousseau’s finished paintings, albeit to a lesser degree than his works on paper, shift abruptly from brooding romanticism (most notably in the canvas, dated ca. 1846–67, that’s based on “The Study for The Forest in Winter at Sunset”) to crystalline, almost storybook naturalism. They are unified solely by their “great plays of light and shadow.” For Rousseau, it seems, style is emotion set free.

The Barbizon School, cited in the exhibition’s title, was a mini-flowering of French painting that bridged Romanticism and Realism. It was named after a town near the Forest of Fontainebleau, where artists gathered during their seasonal painting trips into the woods (Rousseau, a fierce advocate of painting out of doors in all kinds of weather, actually moved to Barbizon in1848 and lived there until his early death in 1867, at the age of 55).

The Barbizon painters, with their practice of direct observation and emphasis on light and atmosphere, were among the first mid-19th-century dissidents to undermine the ”despotic” classical ideal of beauty, in Baudelaire’s famous term, which was imposed on officially recognized art by the French Academy.

Rousseau Rocky Landscape Fontainebleau

Théodore Rousseau, “Rocky Landscape, Forest of Fontainebleau” (ca. 1835-40 [?]), oil on paper, mounted on board, 12 1/2 x 17 inches. Private collection.

Rousseau’s jarringly expressionistic “Study for The Forest in Winter at Sunset” and ”Rocky Landscape, Forest of Fontainebleau,” an oil-on-paper possibly done between 1835 and 1840 — two of the most memorable works in The Untamed Landscape — represent one end of his emotional range, while paintings like the serene ”A Village in the Valley” (ca. late 1820s) are on the other.

In between we find the Turner-esque ”Landscape with Cows and a Fisherman” (no date), in which the clouds, riverbanks, trees and stream all seem to quaver on the point of dissolution, and ”Landscape at Lavigerie, Santoire Valley, Auvergne” (1830), whose slab-like mountainsides could have been painted by Cézanne.

And then there’s the spookily quasi-Symbolist ”Sunset in the the Forest of Fontainebleau” (ca. 1848-50), done in oil and graphite: its composition, funnelling from the gloom of the forest to the half-circle of the sun, glimpsed from a clearing as it dips below the horizon, is entirely drained of color, yet every brushstoke is suffused with the unnatural light of a day-for-night movie shot, a landscape strangely glimmering with the pallor of death.

Rousseau’s stylistic zigs and zags at times venture into less satisfying territory. Some of his pictures, like those of devout peasants or sailboats moored at Granville and Normandy, can be sentimental, fussy, and a bit of a bore. The most roughly made work in the show, “Waterfall in Thiers” (1830), with its hurriedly knifed-in, ill-placed strokes of oil paint, goes markedly slack as your eye moves from the cascading white water to the indifferently brushed-in townscape above. But it also feels seven or eight decades ahead of its time.

It’s intriguing that the most experimental and riveting works in the show were done in the Forest of Fontainebleau, the place Rousseau called home. In ”Rocky Landscape, Forest of Fontainebleau,” mentioned above — another picture that called Kiefer to mind — the image of a blasted-looking field features neither a conventional focal point nor an interplay between major and minor shapes, and in ”Landscape Study, Fontainebleau” (ca. 1855-65), the wildness of the thickets counterpoised by snatches of sky and shimmering swamp water is pushed up a notch by a bizarre, pastel-blue wash isolating a single bush, a flight of invention that seems to come out of nowhere. In the midst of the forest, Rousseau lived what he painted and painted what he lived — a consonance, perhaps, that enabled him to trust the volatility of his vision.

The Untamed Landscape: Théodore Rousseau and the Path to Barbizon continues at the Morgan Library & Museum (225 Madison Avenue, Midtown, Manhattan) through January 18, 2015.

Thomas Micchelli is an artist and writer.