32 ILLINOIS ACADEMY OF SCIENCE. 



Another significant and clarified conception is that of Johann- 

 sen's genotypes. In brief, it is directly opposed to the idea of 

 gradual change through selection, each genotype being permanent 

 and unchangeable. Any selection, therefore, in connection with a 

 single genotype, is ineffective; and when selection has been ef- 

 fective, it means that work was begun with a mixture of geno- 

 types. The practical apphcation of this conception is obvious, 

 and will be referred to later. 



What seems to be another very significant result of the scien- 

 tific work of the last few years, is that obtained by Shull in his 

 work on corn, showing that physiological vigor and yield are de- 

 pendent upon the degree of hybridity. This is related directly 

 to the genotype situation, and is of very large practical import-s 

 ance. 



The third phase of plant-breeding can hardly be called a third 

 period, for it is practically synchronous with the second. As a 

 by-product of the work on inheritance and evolution, some of the 

 scientific results have been applied to practical plant-breeding; 

 and the result has been an expansion of its possibilties that may 

 well be called marvelous. In short, practical plant-breeding is 

 now on a scientific basis; and botany has at last attacked the 

 fundamental problems and may be of some practical service, for 

 it includes plant-breeding. 



Perhaps it may not be out of place to remind you of the large 

 importance of this combination, for it underlies the welfare of 

 human society. It is a combination of scientific research and its 

 practical application in maintaining an ever-increasing food sup- 

 ply over ever-extending areas. If it is the function of medical 

 research and its aplication to provide for the welfare of a cer- 

 tain per cent of the population, it is one of the functions of 

 botanical research and its application to provide for the welfare 

 of the whole population. Nor is scientific plant-breeding, in its 

 restricted definition, the sole contributor to this end, but bound 

 up with it are physiology, ecology, soil investigations, pathology, 

 and the whole round of interests that touch living plants. In short, 

 there is now possible, for the first time, such a co-ordination of 

 scientific results towards a definite end as to make rapid progress 

 possible. 



It may be of service to indicate, by a few illustrations, some of 

 the results of the combination of science and practical plant 

 breeding. One of the first applications to be developed was the 



