1 8 AGRICULTURE 



grown on a different variety. The pollen of a Duchess 

 pear, for example, when it falls on the pistils of a Bart- 



FIG. 17. BRIGHTON GRAPES, SELF-FERTILIZED 



lett pear tree will cause fruit to grow ; but generally no 

 pear develops when the pollen from a Duchess tree falls 



After N. F. State Experimeit Station 

 FIG. 18. BRIGHTON GRAPES, CROSS-FERTILIZED 



on the pistils of another Duchess tree. Trees or grape- 

 vines that act thus are said to have pollen that is impo- 

 tent (powerless) on blossoms of the same variety. Im- 



