SINCE ITS INVENTION by the Cubists early in this century, collage has served as a sharp metaphor for what the modern artist in any field must accomplish. In the twentieth century, to be an artist means to assemble available bits and pieces into a new order. The show of collages by Robert Motherwell now at the Museum of Fine Arts demonstrates the progress of the medium under the hands of one its most skillful practitioners since Picasso. Motherwell's collages, like those of the Cubists or of Kurt Schwitters, attempt to bring a new kind of immediate reality back into painting in place of the new excluded reality of representation. At the same time these works mark stages on the artist's way to defining his own role.

The early works are the most impersonal pieces in this highly personal show, composed not from real world materials but from fragments of paintings and painted imitations of printed patterns. It is as if the artist, this early in his career, could not yet make a whole painting, and instead combined successful forays on the armature of a Cubist model. Some of the works, in fact, are actually renderings or interpretations of Picasso prints in collage. Verbal and literary significances, which permeate all of Motherwell's career as a painter, can be seen as early as Mallarme's Swan, dating from the late forties, and the same inklike shapes that provide the vocabulary of the magnificent later Elegy series are already present in a number of the early collages.

THE ARTIST'S MATERIAL here is taken largely from a set of accidents that are part of his own identity, made formally significant. At times, such gestures as the inclusion of envelopes addressed to Motherwell himself or fragments of programs advertising "I'aventure de I'art abstrait" seem incongruous, amidst the terms of abstract impersonality. For surrounding the bits of cut and pasted everyday material are the gruff lines and shapes of Motherwell's own brand of abstract expressionism. But the elements which move to the forefront are the individual ones: it is the artist's signature which is rendered large and explained by the inclusion of materials reflecting the artist's day-to-day life and basic set of mind.

There is, for example, a peculiar fascination with things French throughout the pieces in the show. A particular brand of French cigarette package is included as the central element of several of the works. On a formal level, this package can be read, along with flattened parcel post wrapping, as the very model of a three-dimensional object being forced into two dimensions. But also, when looked at in conjunction with works titled The French Line, The French Drawing Block, it becomes clear that the formal task is tied, as another part of the legacy of the modern French schools of painting to "the New York school," to a broader idea of "painterliness": For an American in Motherwell's position, to become a painter meant looking to France, to the formal success of its artists but also to their vaguely exotic, elegant charm.

IF all the personal interests peculiar, perhaps only to Robert Motherwell, perhaps to a whole class of painters, can be seen as an extension of the artist's signature, that signature itself plays an important role in a number of the individual collages. These range from the address label of a pasted package to the Reversible Collage signed at the bottom, and again, upside down, at the top. The signature has always been one of the primary signs by which it could be asserted that the picture was something special in the world, and by which the painter could put himself into the picture and make it live. Paradoxical as it may seem amid an art as bare and non-commital as his, Robert Motherwell is able to blend the pieces of these collages not only into a formal conception that succeeds on its own account but probes and experiments with signing himself, in multiple ways, as the artist he wants to be.

NOTABLE EXHIBITS currently at Harvard include the Wertheim Collection now being shown at the Fogg, which includes a number of French late nineteenth century works of astonishing quality. All are carefully chosen, from the Van Gogh self-portrait with its bright green background burning through at the subject's eyes to a Matisse bowl of geraniums that illustrates the gradual way the twentieth century grew out of the advances of the eighties and nineties. There is not a weak or ordinary picture in the group and, together in one room, they provide an excellent area for cross-comparison.

The Busch-Reisinger continues its show on the Swiss painter Ferdinand Hodler for a few days more. Hodler, although respected widely in Switzerland and Germany during his lifetime has been little appreciated here, and on previous stops in New York and Berkeley the show gained attention for Holder as a major new point of perspective in viewing early modernist art. The sketches are the most interesting thing in the show, and most of the larger works appear stiff and stilted by comparison. The landscapes are significant for prefiguring German Expressionist works.

Close on the heels of its tenth anniversary exhibits, Carpenter Center has mounted a show of the year's student work comprising thesis projects in painting, sculpture, photography, and "things we can't even describe," as the poster says. I'm not sure what those undescribables are, but the photography on the main show floor seems to be the most attractive item of the exhibit. John Getsinger has assembled a set of photographs of people in Lowell, along with quotations from the individuals, an explanation of how the photographer came to meet them, and description of their relationships to each other. Maria Schless has produced an excellent series of portraits and sequences of women.

John Barnes's design for a sign system for Widener is also a center of attention. Its components are described on the bottom floor of the Center along with an exhibit of letterings and materials. Of the other works, Couper Gardiner's controlled abstractions are attractive, as is Jon Rikert's Lipchitzian sculpture.