PLANT BREEDING 193 



5. Give examples of plants that " come true to seed " and of others 

 that do not. How does this determine the mode of plant breeding 

 necessary in each case? 



6. How do you account for the fact that there are so many slight 

 differences in long-known varieties of cultivated plants, as Baldwin 

 apj ties, Crawford peaches, Bartlett pears? 



7. Tn saving seed corn of a valuable variety, what can you do to 

 keep the quality up to the highest point? Name several points to be 

 attended to. Send to your state agricultural experiment station for 

 reports upon the change in yield produced by proper selection of seed. 



8. Why is it important for seed corn but not for wheat that plots 

 of different varieties should be kept widely separated. 



9. If you were to undertake to hybridize the following plants, 

 which would be the easiest to manipulate and which the most diffi- 

 cult? Give reasons. Thistle (fig. Ill), willow (fig. 105), arum (fig. 132), 

 grape (fig. 120), corn (figs. 126 and 127). 



10. If you succeeded in hybridizing two species of tulips, A and />, 

 could you propagate the hybrid by planting the bulb matured during 

 that season ? Give full reasons for your answer. 



