Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Polygala' from the website Trees and Shrubs Online (treesandshrubsonline.
A large genus spread over both hemispheres and comprising herbaceous plants, shrubs and a few trees. Leaves alternate, simple, entire; flowers in racemes or spikes; sepals five, the three outer ones small, the two inner ones enlarged and petal-like, forming the ‘wings’ of the flower; petals usually three, united to one another to some extent and forming a keel; stamens commonly eight, united to form a tube. The name is derived from the Greek polys-gala, meaning much milk, some species being supposed to increase the flow of milk in cows.