BOTANY 169 



color and direction and point to every botanical investigation 

 since 1859. 



The richest fruit of the Darwinian theory in the realm 

 of botanical science is the mutation-theory of Hugo de Vries. 

 The theory of Darwin disclosed a method of natural selec- 

 tion, resulting in a survival of the fittest organisms after a 

 struggle for existence; but the origin of the fittest was far 

 from being understood. Here again we find a belated mani- 

 festation of the old Aristotelian modes of thought. Men 

 spun theories and then sought facts to confirm them. The 

 result was a struggle for existence among various hypotheses. 

 But by twenty years of laborious observation Hugo de Vries 

 gave experimental demonstration of one mode of origin of 

 the fittest, one method by which materials for natural selec- 

 tion to work upon are produced. The new plant-form, one 

 of the evening-primroses, was found to arise at once, not by 

 the gradual accumulation of infinitesimal variations, as Dar- 

 win was inclined to believe, but by a single leap or mutation. 

 The result was a mutant, and these mutants were recognized 

 as, in some cases at least, the materials upon which natural 

 selection operates. Whether the natural selection of mutants 

 shall prove to be the universal method of organic evolution, 

 or not, we can not say. Beyond all question of doubt, muta- 

 tion is a fact, and natural selection is a fact, and that selec- 

 tion of mutants does in some cases produce a new species is 

 also a fact. But I feel that a broader statement than this 

 must await the results of the more extended experimental 

 investigations now in progress. 



When Darwin insisted that species arise by natural pro- 

 cesses he was met by the then unanswerable argument that 

 no one had ever seen one species give rise to another. The 

 patient labors of de Vries made it no longer possible to inter- 

 pose this objection. New species were observed to arise from 

 an older one. It now remained experimentally to induce a 

 given species to throw off new forms. This was first accom- 



