Asa Gray was a leading American interpreter of Charles Darwin's theory of evolution. Born in Sanquoit, in central New York, he became deeply interested in botany as a youth. Although he received a medical degree from Fairfield Medical School in 1831, he decided to devote his life to botanical studies, in which field he soon gained an international reputation. Harvard University appointed him Fisher professor of natural history in 1841, a post he held for over forty years. His writings both popularized the subject of botany and advanced it scientifically. Through his correspondence with Charles Darwin in 1856 and 1857, Gray obtained a preview of the theory of evolution by natural selection. When the Origin of Species was published, Gray wrote one of the first reviews, in the American Journal of Science and Arts (March 1860). This review, with several other essays on evolution, was reprinted under the title...