Lysimachia arvensis

Scarlet pimpernel
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Ericales
Family:	Primulaceae
Subfamily:	Myrsinoideae
Genus:	Anagallis
Species:	A. arvensis
Binomial name
Anagallis arvensis L.

Scarlet pimpernel, commonly known as blue-scarlet pimpernel,red pimpernel, red chickweed, poorman's barometer, poor man's weather-glass,shepherd's weather glass or shepherd's clock, is a low-growing annual plant. The native range of the species is Europe and Western Asia and North Africa. The species has been distributed widely by humans, either deliberately as an ornamental flower or accidentally.A. arvensis is now naturalised almost worldwide, with a range that encompasses the Americas, Central and East Asia, the Indian Subcontinent, Malesia, the Pacific Islands, Australasia and Southern Africa.

Traditionally included in the family Primulaceae, the genus Anagallis was placed in the family Myrsinaceae until that family in turn was included in Primulaceae in the APG III system.

This common European plant is generally considered a weed and is an indicator of light soils, though it grows opportunistically in clayey soils as well. The origin of the name pimpernel comes from pympernele [1400–50]; late Middle English, derived from Middle French pimprenelle, Old French piprenelle; Vulgar Latin *piperīnella= Latin piper pepper + -īn- -ine + -ella diminutive suffix.

The flower is most widely known as the emblem of the fictional hero the Scarlet Pimpernel.

...
Wikipedia