The berries are rose hips of Rosa multiflora, an invasive and nasty species of cluster-blooming single white rose (it's from China) with vicious thorns that blooms with a heavy, sweet-fetid scent in early summer.

You can read more about R. multiflora at wikipedia (http://en.wikipedia.org/wiki/Multiflora_Rose) or you can google it for assorted "invasive species" web pages on the subject.