Gray was Torrey’s pupil, swapped plant specimens with him, and assisted him with publication of the ‘Flora of North America.’ Gray and Henry corresponded copiously, as he also did with Engelmann and with Darwin, whose ideas he championed in N. America. Agassiz was a colleague at Harvard, whose creationist views Gray tried to mediate; Muir was a companion on several expeditions. De Candolle (father and son) received Gray cordially on a visit to Geneva. Both Huxley and Owen were met on one of his visits to England: like Gray, important participants in the coming debate about evolution.