Asa Gray (1810-1888) is considered by many to have been America's greatest botanist. His works, which are still considered important, are Structural Botany, The Elements of Botany, How Plants Grow, and How Plants Behave, all published between 1836 and 1879. Gray was a serious critic of Charles Darwin and wrote many letters to him, but was also a firm believer in Darwinian evolution. He was a well-known member of an evangelical Protestant faith, and was effective in countering religious attacks on Darwin by showing that there is no conflict between Darwinism and religion.