Henry Horn came to Princeton as an assistant professor in 1966 in a great wave of new interest in evolution and ecology in the old biology department. This wave was led by Robert MacArthur, and it firmly established Princeton as a major institution in an important awakening of the old disciplines; it rapidly became a world leader and the young Henry Horn became very much part of that revolution.

He came from a large family, a childhood in Virginia and Georgia, and adolescence in Massachusetts, where his father was the pastor of a Lutheran church. Henry not only showed precocious intelligence, but a great interest in nature and the outdoors; he even became an Eagle Scout. He did his undergraduate studies at Harvard University (A.B. 1962) and then went to the University of Washington (Ph.D. 1966). His Ph.D. thesis was a pioneering study on the adaptive nature of the social behavior of blackbirds.

He immediately fit in at Princeton because he not only was a first-rate naturalist, but he had a grasp of mathematics and how the two could meld. These were also the great skills of MacArthur; the two colleagues made a powerful combination. Henry’s intelligence, precocity, as well as sense of humor marked him from the beginning as someone quite special. In those early years he used to have a rubber stamp for the end of his letters which said: Henry S. Horn, Boy Wonder Emeritus.

His research interests were remarkably varied, and always new and original. A common theme was a combination of geometry in conception, mechanical inventiveness in measurement, and “muddy boots” fieldwork in execution. He showed a lasting interest in the growth of trees: how they got their shape, their branching patterns (he even worked on a project started by Leonardo da Vinci, and he extended it very cleverly). Part of his tree work was published in an important book, The Adaptive Geometry of Trees. He also became very interested in the wind dispersal of seeds, and through ingenious experiments made some fascinating observations. Forest succession was another subject he attacked with imagination and clarity. He has had an extended interest in social butterflies and through clever observations and experiments gained some important insights into butterfly behavior.

His impact in the departments (in 1990 biology became the Department of Ecology and Evolutionary Biology, and split from molecular biology) has been large, and of an unusual nature. Beside his contribution in a number of courses—many of them quite original in their approach—his biggest impact was guiding research students, both undergraduate and graduate. To a great degree many of his inventive ideas came into blossom through his students. And it was not only the observation and experiments themselves, but he was a master on expressing them with clarity and insight. He would pepper the margins of the rough drafts with helpful, penetrating comments in clearly printed handwriting. They were often rather severe, but always helpful. He even did this for fellow faculty members, much to their gain. Over the years the number of drafts he has dismembered and then put back together again must be staggering. For him it was a creative process and an enormous benefit to the whole community. This was a large share of his research contribution.

He had founding roles and long-term commitments in several activities outside the department: Alumni Colleges (now Princeton Journeys) of the Alumni Council, summer science workshops for elementary school teachers of the Program in Teacher Preparation, and the undergraduate Program in Environmental Studies of the Princeton Environmental Institute.

He also has another side—an inventive artistic one. He is a fine musician and he and his wife Betty are very involved with the Princeton Chapel Choir and with small-group performances of ancient music. He composes and sings with his guitar very funny verses that make gentle fun of his colleagues, his science, and himself. He also makes striking 3-D wall “paintings,” many with electronic parts salvaged from deceased electronic devices; they are very clever. Perhaps the most memorable one is a fuzzy drawing of Pinocchio partially veiled, but the great nose shows through. “The shroud of Pinocchio” rivals the shroud of Turin. It reflects the many complex but positive attitudes of Henry Horn toward science and toward life.