At first glance, this work might strike the viewer as unfinished, given the blank areas left on the paper. But Cézanne meant Foliage to be a study in color and line depicting the rhythms of rustling leaves, which appear to move across the page. His brushstrokes deliver deposits of pigment that create the illusion of light and shadow. Nature is evoked in the lightness and transparency of the medium, in the placement of the subject, and in the inferred movement.
Cézanne's late watercolors, of which this is a superb example, "are acts of construction in color." Here he applied discrete unblended lines and patches of color around lightly sketched pencil contours and built depth from color by translating dark-light gradations into cool-warm ones. In this mosaic, colored lines and planes and overlapping shades together fix the depth of the subject to the surface of the paper—the white surface that is the final arbiter of pictorial coherence. In this way Cézanne redefined modern drawing according to color "modulation," his term for that which enabled him not only to capture the light of southern France, where he lived and worked, but also to approach abstraction.
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999