OBSERVATIONS REGARDING THE CONSTANCY 

 OF MUTANTS AND QUESTIONS REGARDING 

 THE ORIGIN OF DISEASE RESISTANCE 

 IN PLANTS 1 



PROFESSOR HENRY L. BOLLEY 

 North Dakota Agricultural College 



It is not my purpose to develop a controversy as to 

 theories, but, in pointing out some features of my studies 

 upon disease resistance, it seems necessary to raise some 

 question concerning the rapid development of the muta- 

 tion theory which I believe to be worthy of close thought 

 before we accept this theory as replacing, in entirety, the 

 doctrine of evolution as formulated by Darwin. 



The DeVriesian school has pointed out one way in 

 which plants and animals originate new individuals with 

 characteristics apparently new. The Mendelian formu- 

 las, especially as in late years developed, illustrate clearly 

 how apparently new characteristics may appear to be 

 caused to arise. This would seem to be a fair statement 

 of all that has actually been accomplished. 



I assent that most of the conceptions arising from the 

 investigations of Mendel and DeVries are probably cor- 

 rect and, after considering expositions depending upon 

 the experiments of many workers and having experi- 

 mented sufficiently to understand the meaning of " mu- 

 tants," "unit characters" and "elementary species," I 

 recognize that these works added much light upon how 

 evolution in plant life takes place, and that henceforth 

 the conception of unit characters must largely form the 

 theoretical working basis for practical breeding work. 

 Yet I feel sure that Darwin's conception was sufficiently 

 broad to embody both features as minor parts of the 

 great concept of organic development. To accept De- 



1 Read before the American Breeders ' Association, Washington, D. C, 

 January 29, 1908. 



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