The idea that a plant contains within it some sign or 'signature' from God that gives a clue to it's potential use . Such beliefs have been popular at some point in most cultures around the world and are still apparent today.
Examples:Yellow plants for jaundice.
Red plants for blood.
Fruits shaped like genital organs to promote fertility .
Lungwort (Pulmonaria officinalis) with white blotches on the leaves resembling alveoli or possibly mucus build-up in lungs has a traditional use as an expectorant.