V. sororia or V. papilionacea or V. cucullata?
I was hiking in the Pere Marquette State Park outside Grafton Illinois (along Illinois R.) and saw a wonderful carpet of violets throughout regions of the park. The question is, which of the above is most likely. The leaves were scallop-edged, heart shaped and lightly haired on the underside.The flower stems also had detectable hairs, but weren't exactly furry. The flowers were borne above the leaves and had hairs on the lateral petals. Is there any reliable way to tell these apart without a magnifying lens to check whether the petal hairs are "short and thick" or "longer and thin?"
Note: the terrain on this terrain is forested and hilly, with lots of rock escarpments. Other flora included oaks/hickories, redbud and dogwood, some river birch in ravine bottoms. Smaller plants like fragile and Christmas fern, May apple, and spring beauty were also plentiful.