Asa Gray published two important works that dealt with South American plants. His monumental work of plants of the Wilkes expedition, largely from the South Pacific, enumerated 1,052 species in 557 genera of 83 families of dicots. It included 246 new species, 17 new genera, 48 new combinations, and 26 varieties. The second major work, in collaboration with Joseph Dalton Hooker, discussed disjunctions in general and provided 88 examples of North-South American disjunction. This amphitropical disjunction is briefly presented, with key references cited. Several new examples from the Brassicaceae are presented for the first time, and they demonstrate the three major North-South American amphitropical disjunctions proposed by Peter Raven in 1963.