Whatever else you can say about it, “The Thaw Collection of Master Drawings: Acquisitions Since 2002” offers instructive examples of how artists have dealt with the challenge of drawing foliage. Do they depict it en masse or one leaf at a time? As impressionistic mélange or botanical artifacts? The forest or the trees? The nineteenth-century German engraver Heinrich Reinhold bridged the gap by honing in on the specificities of this leaf or that vine within a broader orchestration of tangled branches. Adrian Zingg, Reinhold’s Swiss contemporary, codified nature by transforming it into jagged shards of patterning. In a spare and scratchy ink drawing circa 1790, Jakob Philipp Hackert rendered foliage as an electrical current. One hundred years later ...