Wood anemone (Anemone nemorosa)
Collins, 80; Readers Digest, 27
This delightful spring plant is a welcome sight in many woods across the region, from March to April. At night and under cloud the flower head droops but will awaken when the sun shines. The plant prefers deciduous woods and coppiced plantations since it requires sunlight. The underneath of the flower has a pinkish hue.
See also: http://www.botanical.com/botanical/mgmh/a/anemo036.html
With a common dog violet