They discovered that trees gave off essences and scents, called phytoncidere, which protect the trees by killing germs and diseases.
原來森林中不同樹木會散發不同的精氣與香氣，叫「芬多精」，這是森林植物為保護自身所散發出的一種揮發性物質，可以殺死空氣中的細菌、黴菌、病毒，並防止寄生蟲侵害樹體。