Augustin Pyramus de Candolle (1778-1841) was a Swiss botanist. Candolle's botanical career began by working at a herbarium. Within a couple of years he had established a new genus, and went on to document hundreds of plant families and create a new natural plant classification system. Candolle's main focus was botany, but he also contributed to related fields such as phytogeography, agronomy, paleontology, medical botany, and economic botany. Candolle originated the idea of "Nature's war", which influenced Charles Darwin and the principle of natural selection. Candolle recognized that multiple species may develop similar characteristics that did not appear in a common evolutionary ancestor; this was later termed analogy. During his work with plants, Candolle noticed that plant leaf movements follow a near-24-hour cycle in constant light, suggesting that an internal biological clock exists. He died in 1841 after being sick for many years.