At Sebert County Park, I stumbled across American Dog Violet (Viola conspersa). This handsome blue violet is uncommonly encountered in moist woods, mostly east of the Mississippi River.
Limestone Bittercress (Cardamine douglassii) was flowering at Spicer Lake Nature Preserve. This plant of the mustard family (Brassicaceae) is commonly found in moist woods, often in somewhat disturbed areas.
The flowers of Limestone Bittercress have four petals, characteristic of mustards. This species is similar in appearance to Bulbous Bittercress (Cardamine bulbosa), but as you'll notice in the photograph below the stem within and below the inflorescence is pubescent, while that of Bulbous Bittercress has no hairs. There are also habitat differences, as Bulbous Bittercress is more often found in springy areas.