BETTER PLANTS AND ANIMALS 



yellow or green) and in the shape of the ripe seeds (whether 

 smooth or wrinkled). Mendel then discovered that if he crossed, 

 for example, a plant bearing smooth peas with a plant bearing 

 wrinkled peas, the hybrid plant coming from such a cross would 

 bear all smooth seeds. He also found that other pairs of charac- 

 ters with which he experimented behaved in a manner similar to 

 the behavior of the smoothness or wrinkledness of the seeds of 

 peas. In the first generation 

 one character dominated and 

 appeared alone, apparently 

 to the total exclusion of the 

 other. In this first gen- 

 eration, however, it was sup- 

 posed that in reality the 

 character not appearing was 

 actually present but was 

 hidden by the so-called dom- 

 inant character. The charac- 

 ter thus hidden is called the 

 recessive character. 



It was found by further 

 experiment with plants and 

 animals that certain char- 

 acters are always dominant 

 in the first generation, while 

 others are always recessive. 

 For example, when tall- 

 stemmed and short-stemmed 



pea plants are crossed, the tall-stemmed character is dominant 

 in the offspring of the first generation. When pea plants bear- 

 ing their flowers along the stem are crossed with those which 

 bear their flowers bunched at the end of the stem, the offspring 

 all bear their flowers along the stem, the character of bearing 

 the flowers at the end of the stem being recessive. When 

 bearded and beardless wheats (Fig. 9) are crossed, the first gen- 

 eration is beardless. Long-staple cotton crossed with short-staple 



FIG. 9. Smooth and bearded wheats 



When smooth and bearded wheats are crossed, 

 all the heads in the first generation are smooth 



