"The progress of botany, as of other sciences, comes from the interaction of so many factors that undue emphasis on any one can give a very distorted impression of the whole, but certainly among the most important of these for any given period are the prevailing ideas and intellectual attitudes, the assumptions and stimuli of the time, for often upon them depends the extent to which a particular study attracts an unbroken succession of men of industry and originality intent on building a system of knowledge and communicating it successfully to others of like mind."