From her photograph, Fernande Olivier hardly appears a likely muse for the 20th century’s most influential artist.

In the black-and-white picture, a simple dress hangs loosely over sloping shoulders and sagging breasts. Her neck is thick. An awkward depression mars the area above her upper lip. And luminous eyes — her one beauty — are nearly obscured by a drooping knot of hair arranged tam-o’-shanter-like over her brow.

And yet “la belle Fernande,” as she was known, would be Pablo Picasso’s first serious romantic companion, as well as the template for more than 60 works the artist created during an eight- to 10-month period in 1909.

Presented for the first time in a single- subject exhibit — “Picasso: The Cubist Portraits of Fernande Olivier,” now showing at the National Gallery of Art — these works are anything but traditional exercises in portraiture.

Olivier’s involvement in Picasso’s life, after all, came during a period of seminal change in the Spaniard’s career — when he and his colleague, the French artist Georges Braque, pioneered an entirely new form of artistic portrayal composed of “little cubes,” which eventually evolved into cubism. Elements of Olivier’s likeness — mouth, hair, face and bust — appear as a motif woven through a series of early cubist experiments.

“I think her influence on his work was very small,” said curator Jeffrey Weiss. “It’s really about process.”

The three-room exhibit, which is organized chronologically, commences with a series from the spring of 1909 titled “Head of a Woman,” where five nearly identical semi- cubist outlines are filled in with varying degrees of clarity and color. Here, Picasso’s fascination with African masks is clearly demonstrated in the crude brush strokes and hollow-eyed depictions. Nearby, however, a set of seated nudes shows Picasso playing with aspects of a lumpy female form, practically devoid of cubist inclination.

As the work takes on a progressively more angular air, Picasso homes in on Olivier’s nose, mouth, ears and eyes in a grouping of studies, portraying these features in planes of fractured form — forms which are then fitted like puzzle pieces into several portraits from this time.

During the summer of 1909 Picasso and Olivier traveled to the Spanish village of Horta de Ebro, where Olivier apparently fell ill with a kidney infection and was in poor spirits. It was here that Picasso completed much of the exhibit’s oeuvre and would also photograph several Olivier canvases in his studio, arranged in different sequences against a wall. The effect has an eerily Darwinian quality to it — with the images of Olivier mutating into decidedly different artistic forms and views.

In several of the images created during their stay, a tilted, downward-looking head imbues the figures with a sense of melancholy. This may have been an effort to reflect Olivier’s dyspeptic mood, Weiss said, or merely an attempt to draw on an artistic tradition dating back to the Middle Ages. Later, the technique pops up again in more abstract, cubist works from the fall of 1909, possibly as a means to give his increasingly fractured portraits some degree of emotional content, Weiss said.

While a somberness overlays much of this work, a rare exception is the ink-and-pen sketch “Female Nude with Raised Arm,” in which a tiny figure flings her arm upward in a humorous homage, one could imagine, to the curative powers of Jazzercise.

Throughout 1909, Picasso vacillates between figurative depiction and incipient cubist imagery, with some of the resulting hybrids low in beauty, yet oddly compelling.

A handful of these paintings hark back to the part-man, part-beast beings found in H.G. Wells’ sci-fi classic, “The Island of Dr. Moreau.” There is a decidedly simian quality to the faces in two later versions of “Head of a Woman” and in “Woman with Pears,” where bizarrely configured facial features come together in a pinch of earth tones. The bronze cast of “Head of a Woman (Fernande)” — whose recent acquisition by the gallery served as the inspiration for the exhibit — invokes Picasso’s lover with the ruffled crest of a rooster.

At some moments in the exhibit, Olivier is entirely lost in Picasso’s total embrace of his new technique. Prominent among such paintings is “Woman in an Armchair,” a shadowy, chiaroscuro cubist rendering, which divorces the viewer from the image in much the same way a suit of armor obscures a lady’s knight and with similar visual results.

Still, in other works from the latter part of 1909, Picasso seems to reject the cubist trajectory on which he was traveling. Both the small pencil sketch “Head of Fernande, Casket and Apple” and “Woman with a Mustard Pot” reflect more traditional notions of physical representation.

“What’s going on is a certain amount of advance and retreat,” Weiss explained. “As a result you can find him retreating into realms of realism and naturalism along the way.”

Taken as a whole, the 54 works presented here are all about one man’s artistic growth. Development is never without some pain — a quality that comes across in the sometimes brutal portraits which comprise the show. As such, the Olivier series will be of especial interest to those concerned with how an artist approaches and manipulates images in the course of creating new pictorial techniques.

Though her essence lingers on the canvases, Olivier, the woman, was clearly as secondary a factor in the process of Picasso’s artistic evolution — whether the artist’s model even “sat” for any of these works remains to be seen — as she ultimately proved in his personal life.

In 1912, after a mercurial, eight-year relationship, Picasso, ever the inveterate womanizer, would leave Olivier for Eva Gouel. Olivier, like the many women who would follow in her footsteps, was said to be devastated.

“Picasso: The Cubist Portraits of Fernande Olivier” runs through Jan. 18, 2004, in the National Gallery of Art’s East Building. For a complete listing of gallery talks and other activities related to the exhibit, go to www.nga.gov.