The origins of the spiral theory of phyllotaxis

Abstract

In September 1829, at the Convention of German Scientists and Physicians at Heidelberg, two young botanists, Carl Schimper and Alexander Braun, presented papers outlining a new theory describing the distribution of leaves around an axis, or, to use the botanical term, phyllotaxis.' The theory broke with past writings on the subject in two essential respects: it postulated that all leaf distribution should be understood as a spiral and, more importantly, that all possible spiral variations may be defined by the fractions of several mathematical series well known to students of the theory of numbers. Although their fellow botanists applauded the originality and elegance of the spiral theory, not all of them would accept it in the form that Schimper and Braun proposed. Auguste and Louis Bravais wanted to revise the theory for empirical reasons, suggesting some numerical values slightly different from those of Schimper and Braun.2 Julius Sachs mistrusted the theory for epistomological reasons; to him it seemed to lack a satisfactory causal explanation and was too heavily laden with fanciful numerology.3 Though twentieth-century scientists have paid