194 Plant-Breeding 



one or more characters, and (c) recombination of existing 

 characters. 



If the mutation is due to the addition of a new char- 

 acter and it remains constant, there must be present in 

 its germ-cells some unit to represent that new character as 

 there was in the gametes of the parent which produced it. 

 Likewise, if a character is lost, its germinal potentiality 

 must have become lost or entered into a latent condition. 



If mutations of these types are crossed, the new gametic 

 representatives or absences in the case of a lost character 

 become pure in the germ-cells and reappear in the next 

 generation. Hence they are not lost. 



If the mutation has a hybrid beginning and is due to 

 an unusual combination of characters, this condition can- 

 not be lost, as this certain combination which has once 

 occurred will reproduce true if it is homozygous, or if not, 

 it having occurred once may appear again through a like 

 combination of unit-characters even though crossing and 

 amphimixis may have taken place. 



Mendelism in wheat. As a specific example of evident 

 mendelian results, W. J. Spillman, agriculturist of the 

 Department of Agriculture, here explains some of his ex- 

 periments with wheat. 1 Mr. Spillman independently dis- 

 covered numerical results, before the knowledge of the 

 mendelian experiments had become generally known. 



"The photograph (Fig. 47) shows three generations of 

 one of my hybrid wheats. Of the three heads in the 

 upper row, the left-hand one is the male parent (variety 

 Valley) ; the right-hand one is the female parent (variety 



1 Published in fourth edition of this work, 1906 ; and here reproduced 

 nearly entire for its historical as well as for its plant-breeding value. 



