PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 321 



in all instances, either in the first generation or in succeeding 

 ones. 



The discovery of mutation shortly before our period, to- 

 gether with Mendelism, has awakened biologists as nothing else 

 has done in recent years. Unexpected variants or sports had 

 been recognized as starting points in securing desirable plants, 

 and it is now supposed that they are either mutants or hybrids. 

 Experimental evolution and breeding have to do with both 

 hybridization and mutation, but neither biologists nor breeders 

 have discarded continuous variation as a possible explanation of 

 the evolution of new forms. Much as mutation and Mendelism. 

 both dependent on unit characters, have done for plant breeding, 

 we still believe that there are characters other than unit characters 

 and variations other than those accounted for by the two new 

 theories. Of course useful variations are equally helpful to 

 the breeder, whatever their origin, nor is there certainty that 

 mutation and ]\lendelism can maintain their |)rominence in- 

 definitely. 



Physiological chemistry may yet aid cytology greatly in 

 solving problems of heredity, even to the extent of helping to 

 determine the role of various elements of the protoplast. Chem- 

 istry may help to determine whether chromosomes or ultra- 

 microscopic bodies, as the hypothetical genes, chromioles, or 

 pangens, are the carriers of heredity. However this may be, the 

 recent tendency is away from the view that any theory of car- 

 riers of heredity involves a belief in preformation. 



Mass selection, commonly practiced under the empirical 

 methods of breeding, is now known to result in composite strains. 

 Consequently, this crude method is gradually giving way to in- 

 dividual selection, by means of which we may obtain desirable 

 pure strains. By individual selection, it has been demonstrated 

 recently that hundreds of types may be segregated from single 

 varieties of cereals. This information places us at the threshold 

 of almost limitless possibilities in breeding certain plants by 

 selection. 



Ready facilities in transportation and increase in city popu- 

 lations conspire to make plant breeding more profitable from year 



