Eyebright

I was photographing plants on the limestone pavement at Gait Barrows National Nature Reserve this afternoon. Many are very rare, but we're well past their best this late in the summer. On sorting through the photos, this very common Eyebright was the one that stood out. It is one of around 20 species of the genus Euphrasia recorded in the British Isles. They are semi-parasitic annual plants found in almost any patch of grassland, heath, dune or rocky place. This one could be a special species from limestone areas, but I don't have any ID books with me and they are notoriously difficult to sort out.
The genus historically has been a traditional cure for "all evils of the eye". It has been commonly used in folk medicine Ada treatment for blepharitis and conjunctivitis, but is now thought to be neither efficacious or safe!