Scarlet Pimpernel
Anagallis arvensis

Scarlet pimpernel flowers only open when the sun shines; their habit of closing in dull weather has given the plant the name 'poor man's weather-glass'. It is a plant with a long history of use in many countries and has been used for neurological disorders including depression and madness. The genus name "Anagallis" comes from the Greek name Anagelao "to laugh" because of its use among the ancient Greeks for depression. It was once considered a universal cure for all: "No heart can think, no tongue can tell, the virtues of the Pimpernel".