Relationships between the individual and the communal component of artistic achievement bedevil every generation. T.S. Eliot insisted that every innovation gestates in an affinity with indispensable predecessors. Robert Musil declared,”It is only meaningful to speak of originality where there is a tradition.” Much as we love the romance of radical breaks, modernism itself evolved from roots in previous tendencies.

The innovations of Arthur Dove (1880-1946) are inconceivable without Cezanne, Kandinsky, Matisse, Picasso, and, especially, Picabia. A valued member of the Stieglitz circle, Dove was in close sympathy with Georgia O’Keefe and the American painters who clustered around Stieglitz’s Gallery 291.Yet out of creative affinity with the work of other modernists came a distinctive achievement that made Dove an American original. And a national treasure.

Dove began his career as an artist around 1903, the year he graduated from Cornell, where he had studied law. Soon after he moved to New York, his work was appearing in masscirculation magazines and he was dining at Mouquin’s, a Gilded Age restaurant popular with John Sloan and others of the “Eight.” He married and, after four years as an illustrator, left for Paris.There he made friends with Alfred Maurer, a frequent visitor to Gertrude Stein’s salon, and exhibited in the Salon d’Automne of 1908. He and Maurer went on sketching trips outside the city, often to Cagnes, in the south. Dove was a rural modernist, closer in spirit to Cezanne than to the urbanites who were his friends.The earth – its tones,distances,and undulations – provided impetus to paint.

Back in the States by 1909, he moved to Westport and bought a chicken farm to support his family.The labor was grueling; his marriage collapsed under the strain. In 1921, he moved into a houseboat moored off Manhattan with his companion, the painter Helen Torr. The pair eventually settled on the North Fork where he continued to raise his own food, a precarious livelihood supplemented with stipends from Stieglitz and, later, Duncan Phillips.

Dove did not commit himself to watercolor until 1930. Its translucent liquidity suited his need for what he called “a means of expression which did not depend upon representation … [but was] nearer to the music of the eye.” The crystalline light of watercolor wellhandled evoked what he referred to as “sensations of light from within and without.” He took readily to the medium, producing one or two a day.

The exhibition at Alexandre Gallery displays a comprehensive gathering of Dove’s watercolors, produced in the last decade-and-a-half of his life. It includes sketchbook pages and a select group of works from the Dove estate never before exhibited. These radiant little works (most of them 5 inches by 7 inches, later ones 3-by-4 or 3-by-5) distill his move toward abstraction while continuing to suggest organic forms and the diurnal brightness of the natural world.

“Sunrise” (1937) and “Clamshell,” both beautifully elliptical and spare in drawing, typify the process of simplification in which medium and color became the essence of his imagery. Unconstrained by the conventions of landscape painting, “Wooded Pond”(1935) summarizes Dove’s characteristic tension between empathy with the natural world and a bent toward full abstrac tion. The fluidity of the paint and the speed of the brush dabbing wet-in-wet suggest a locale – a broken downward stroke for a tree, a single horizontal one for the water’s edge – without depicting it. Its subject is the fugitive mood of the place, a turbulent metaphor for the inner life of the artist observing it.

The jagged spiral of “Willow Tree” (1938) lets the pale green and white of the willow’s downy leaves stand for the tree itself.The first American to produce an uncompromisingly abstract painting as early as 1910-11, Dove earned Duncan Phillips’s proclamation that he was “the boldest American pioneer.”

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The game rules of art have changed frequently over the last century, but certain constants keep reasserting themselves between shifting goal posts. One of them is the importance of proportion, an intimate component of all other design principles. Mathematical recipes have been devised for it, yet it remains largely indefinable and intuitional. Arthur Wesley Dow, in his classic text “Composition,” called it “the mystery of Spacing.”

That mystery is at the heart of Sal Federico’s elegant two-color compositions, which are stripped bare of representational references. In each, a single hard-edged, free-form angularity painted in one solid color hovers over a flat field of another, often contrasting color. There is a heraldic aura to the work, each painting a postmodern hache d’armes.

Mr. Federico favors mural-sized dimensions. Size creates sensory impact, but scale, a matter of internal proportion, is the critical formal element. Perfectly scaled works – as are the ones on view at George Billis Gallery – do not require the additive of size. The artist’s prints and smaller works are as satisfying as the large canvases.

Mr. Federico plans his compositions on a hexagonal grid to insure that slants harmonize and angles repeat accurately. The central form of “Calepodius” (2005), pure cadmium yellow and notched like a pole-axe, is beauti fully poised on a field of yellow green. The design, named after a third-century Roman martyr, suggests a crest emblazoned with the blades of martyrdom. “Praxedes” (2005) plays with a single tri-vectored device and its mirror image. Each bright blue variant lies rampant, count-rampant, and at differing tilts across a white field.

The two azure forms of “Agatha” (2005) appear identical at first. But look again. The lateral notches of each are in different positions on the invisible underlying grid. One set of indentations slims the form at its center; the other expands it. Together, they testify to the enigmas of good spacing.

My favorite is “Hannah” (2005). Three identical, indented forms, each a different tone of blue, rise from a saturated yellow field.The axis of the forms and the spatial cadences evoke living movement – are these larks ascending? Chivalric eagles? Beauty lies not in what we make of it but in the inventive use of symmetry and repetition.

Dove until June 16 (41 E. 57th Street, between Madison and Park Avenues, 212-755-2828). All works are on loan and not for sale. Federico until June 10 (511 W. 25th Street, between Tenth and Eleventh Avenues, 212-645-2621). Prices: $950-$7,500.