Autumn, Poplars, Eragny; Camille Pissarro
Link is to zoomable version on Google Art Project; downloadable file on Wikimedia Commons; original is in the Denver Art Museum which also has a zoomable version (and, oddly, has another, somewhat different looking version of the image).
This is Pissarro at the height of his classically Impressionist style. The painting is composed of individual dabs of intense color, intended to be blended optically when viewed from the proper distance.