From the concept of the ur-plant Goethe soon learned to develop another concept which was to express the spiritual principle working in a particular plant species, just as the ur-plant was the spiritual principle covering the plant kingdom as a whole. He called it the type. In the manifold types which are thus seen active in the plant world we meet offsprings, as it were, of the mother, the 'ur-plant', which in them assumes differentiated modes of action.