I agree with dave. Even being a cartoon plane the curve of the wing looks a bit odd. It should be straight from the wingroot (against the fuselage) to the tip of the wing. It's hard to tell from the reference you posted because it doesn't have a front view but if you look around on the web you'll see that the p-36 has a straight wing (wikipedia has some decent photos). If you wanted to make a gull-wing (similar to the F4U Corsair) it would be straight from the wingroot to the point where it angles upward and then straight to the wingtip.

I might be biased though, having worked on planes for 4 years and being an avid plane-buff since I was old enough to care.