18 



THE ESSENTIALS OF AGRICULTURE 



first supposed, but that a given character is present in the one 

 case and absent in the other case. When the cross is made, the 

 character present in one parent goes into the hybrid, while the 

 other parent does not contribute anything to that character. 

 Consequently the one character is dominant in the sense that 

 it is present. For example, in the case of smooth and wrinkled 

 seeds the smoothness is due to the presence of a ferment, or 

 enzyme, in the seeds, which changes the sugar in the growing 

 seed into starch, whereby the seed is more perfectly filled out 

 and is consequently smooth. In the case of the wrinkled seeds 



this ferment is ab- 

 sent, the sugar re- 

 mains unchanged, 

 and since the cells 

 are not filled with 

 solid starch grains 

 but with a watery 

 sugar solution, the 

 seeds, on drying, 

 shrivel and hence 

 become wrinkled. 

 In the case of 

 green seeds in 

 peas an enzyme 

 destroys the green 



material known as chlorophyll and leaves only the yellow color ; 

 therefore the seeds are yellow. In the case of green peas the 

 enzyme is absent ; hence the yellow color is obscured by the 

 green color and the peas appear green. 



In a word, Mendel found that a plant (and the same has since 

 been found true of animals) in respect to its characters is, as it 

 were, like a child's playhouse, constructed of many different 

 shapes, kinds, and colors of building blocks, which can be taken 

 to pieces and put together again in a new way, so as to make 

 a structure entirely different in appearance, although built from 

 the same materials. The house is the plant or animal, and the 



FIG. 12 a. Razorback, or unimproved hog 

 Matures slowly, and is less valuable when mature 



