The Cuckoo Flower (Cardamine pratensis) appears just a bit earlier than the cuckoo and it grows under trees or along a walking track, in a grassy not too dry spot where it can get some sunshine. Here it brightens up a little wood near a small stream.
It belongs to the Brassicaceae family, like kale, rape and also most of the little white flowers you find now everywhere in flower (see Little white jobs). The four petals are slightly veined.
You have to hurry to see it in flower, its season is short !