PLANT IMPROVEMENT 



appeared in a field of Fultz, in 1865. The Rudy originated 

 in a large field of wheat near Troy, Ohio, in 1871. The Con- 

 cord grape, nectarine, navel orange, and many other valuable 

 kinds of fruit probably originated 

 in a similar way. 



Improving plants by crossing. 

 In order to understand crossing 

 or hybridizing, it will be neces- 

 sary to review briefly the way in 

 which plants produce seed. For 

 this review we shall begin with 

 the flower. The essential parts 

 of the flower are the stamens and 

 pistil. Each stamen has at its 

 end a small sack containing 

 minute structures called pollen 

 grains. The pistil is enlarged at 

 its lower end, forming the ovary 

 in which one or more small bodies 

 are located from which seed are 

 developed. But these bodies are 

 unable to develop into seed with- 

 out the aid of pollen. A pollen 

 grain which may happen to lodge 

 on the upper end of the pistil, 

 called stigma, sends an out- 

 growth like a slender thread, 

 called pollen tube, down the neck 

 of the pistil into the ovary. A 

 small part of the pollen substance passes down this thread, 

 or pollen tube, and when it reaches the ovary unites with the 

 seed-producing body inside. This union is called fertili- 



Embryo sac of lily showing 

 fertilization taking place. 



A. Pollen tube. 



B. Egg. 



C. Fertilizing element (nu- 

 cleus) from pollen tube uniting 

 with B. From the cell produced 

 by this union the germ of the 

 seed develops. 



