 Geoffrey was from England, both better trained and more intelligent than I was.He read Peter Mitchell’s paper, came to me, and said ‘André, could this possibly explain XE [something that preceded ATP formation]?’"

As a result of this conversation, Jagendorf began to communicate with Peter Mitchell who invited him to visit his lab so that he could learn about the chemiosmotic hypothesis.Later that summer Jagendorf did the "experimentum crucis" that showed that the synthesis of adenosine trisphosphate by chloroplasts depended on the magnitude of the pH difference.