RELATION OF BIOLOGY TO AGRICULTURE 549 



principle. No new categories of variations, but an illuminating demonstration 

 of the possibilities of stimulating variability and of the reality of this general 

 variability as the fundamental transforming factor. No new evidence either to 

 help the Darwinian factors to their death-bed, or to strengthen their lease on 

 life, for the " man " factor in all the selecting phenomena in Burbank's gardens 

 excludes all natural factors. 



Most of Mr. Burbank's creations are originated by the crossing of 

 existing forms. In a large number of hybrids there is almost a cer- 

 tainty of their being some chance individual of useful character. " In 

 one year he burned up 65,000 two- and three-year-old hybrid seedling 

 berry bushes in one great bonfire, and had fourteen others of similar 

 size." 



About the same time that the Mendelian law was rediscovered the 

 word mutations came into use, and it is such a useful word that it is 

 now widely used outside of biology. The fact that plants and animals 

 produce distinctive characters not connected with the ordinary form by 

 intermediate stages is perhaps of greater importance than any other 

 announcement since the publication of " The Origin of Species." Al- 

 though in a sense opposed to Darwin's conception, the examination of 

 the change in species through mutations as given by de Vries would, in 

 all probability, have been most warmly received by Darwin, because it 

 is a reasonable amendment to his maturest attempt to enunciate the 

 laws of nature. 



The fact that mutations do occur, and that they may properly be 

 considered the foundation of elementary species or varieties, as shown 

 by de Vries, is of the highest economic significance. It is only through 

 procedure based upon this principle that lasting results have been ob- 

 tained by even the most careful selection and improvement of farm 

 crops. Because of the violation of this principle, much conscientious 

 effort has failed to originate even a single variety of lasting value. 



We now recognize that in the creations available we have the be- 

 ginnings and the possibilities of all we seem likely to want or need in 

 the way of new varieties or types of plants or animals. 



From a field sown with a supposed pure variety of Swedish barely, 

 Mlsson has isolated and established a number of separate and distinct 

 types, each one having some features of utility that renders it superior 

 to the crop formerly grown in the locality for which it was designed. 

 Here, too, the "man" factor was the chief factor. Nilsson's work 

 especially suggests that the beginnings of all we need are to be found 

 by those who have the skill and the diligence to detect and use them. 



In a similar instance, a worker in an American experiment station 

 has isolated a number of types of cotton of distinct usefulness from a 

 field of what had been regarded as a standard variety. 



This conception of the origin of varieties emphasizes the single in- 



