Goethe’s archetypal plant. understood first as a literal historical ancestor to all plants (which may well have existed at some point), and later as the schema of ‘plantness’

With this model and the key to it, it will be possible to go on forever inventing plants and know that their existence is logical; that is to say, if they do not actually exist, they could, for they are not the shadow phantoms of vain imagination, but possess an inner necessity and truth.