PREFACE. 



The belief that we must look mainly to the environment 

 as furnishing the influences which induce plants to vary- 

 in response to them — whereby adaptive morphological 

 (including anatomical) structures are brought into exist- 

 ence — appears to be reviving. To illustrate the progress 

 of this belief, I will give a few cases. 



In 1795, Geoffroy Saint Hilaire "seems to have 

 relied chiefly on the conditions of life, or the ' monde 

 ambiant,' as the cause of change." * 



In 1801, Lamarck "attributed something to the direct 

 action of the physical conditions of life " as the means 

 of modification, " something to the crossing of already 

 existing forms, and much to use and disuse," 



In 1831, Mr. Patrick Matthew (who, like Dr. W. C. 

 Wells in 1818, anticipated Mr. Darwin in the theory of 

 "natural selection") "seems to have attributed much 

 influence to the direct action of the conditions of life." 



• I quote from Mr. Darwin's " Historical Sketch " in his Origin of 

 Species, 6tb ed., 1878. 



