DABWIN'S INFLUENCE UPON PLANT 

 GEOGRAPHY AND ECOLOGY 



PROFESSOR FREDERIC E. CLEMENTS 

 University of Minnesota 



Darwin dealt with plant geography only incidentally 

 in connection with origin by descent. He was concerned 

 chiefly with the bearing of migration upon community 

 of origin, and consequently with the question of single 

 and multiple origin of species. In his discussion of mi- 

 gration is found some consideration of barriers, endemism 

 and isolation, but only in so far as these contribute to his 

 main theme. On what might be called the ecological side 

 proper, i. e., the response of the individual, Darwin made 

 his greatest contributions. Leaving apart his studies of 

 pollination, movement and insectivorous plants, the ecol- 

 ogist must consider his fundamental work in variation 

 and adaptation, together with his conclusions upon the 

 questions inseparably connected with them, namely, com- 

 petition, selection, inheritance of acquired characters and 

 mutation. 



In estimating Darwin's influence in all these matters, 

 I have endeavored to keep in mind three view points: 

 (1) his exact opinion upon each question, (2) his actual 

 contribution to it, and (3) his share in our present knowl- 

 edge of the subject, as well, perhaps, as his influence in 

 shaping our present opinions where they do not rest on 

 experimental knowledge. Several inherent difficulties 

 have manifested themselves during this attempt. Chief 

 among these is the impossibility of ascertaining what 

 might be called the majority opinion of botanists, a diffi- 

 culty aggravated by the fact that no two botanists would 

 draw the same line between what is proved and what is 

 merely held. In addition, Darwin's own views seem to 

 have remained plastic to a degree not always evident in his 

 most widely read books. This has brought the curious re- 

 sult that his earlier views have often had much the greater 

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