"Common toadflax (Linaria vulgaris) is a curiously shaped flower that gives rise to the name 'cod's head' in Norwegian, and in dialect nomenclature it has been likened to a variety of other animals' mouths: dog, rabbit, mouse, lion, monkey and so on. Its colouration accounts for the alternative English name of butter-and-eggs; the eggyolk-orange part gets darker as it matures. The plant can become very invasive and is regarded as a weed. Being hard to distinguish amongst true flax until it flowered it was awarded a pejorative affiliation with toads."