植物像其他所有形式的生活一样发展，他们提出了自己的侵略，防御等形式。在19世纪，大多数理论涉及牙齿和爪上的动物天然红色。但是现在科学家正在思考根和茎中的自然绿色。我们意识到，在不断生存的努力中，植物已经演变为从与其他动物的复杂共生到信号机制到警告其他植物的一切，再到彻底的化学战。
(Plants evolve like every other form of life, and they've come up with their own forms of aggression, defense, and so on. In the nineteenth century, most theories concerned animals-nature red in tooth and claw, all that. But now scientists are thinking about nature green in root and stem. We realize that plants, in their ceaseless struggle to survive, have evolved everything from complex symbiosis with other animals, to signaling mechanisms to warn other plants, to outright chemical warfare.)