278 



General Botany 



true when planted. Seeds from self-pollinated corn do not pro- 

 duce the most vigorous plants and the largest yields. The best 

 corn seed is obtained by planting in rows and removing the 

 tassels (the staminate flowers) from alternate rows. The seed 

 for the next year is then collected only from the detasseled plants. 

 In this way the breeder is assured that the pollen came from another 

 plant and that the plants grown from these seeds will have the 

 increased vigor that is characteristic of cross-polhnated corn. 

 Sunflowers are not self-fertile. That is, even though pollen does 

 fall on a stigma of the same flower cluster, fertilization does not 

 occur and no embryo is formed. In plants of this type pollen 

 must be carried from one plant to another. These three examples 

 illustrate some of the details of reproduction with which the plant 

 breeder must be famihar before he can intelHgently engage in 

 plant-breeding work. 



Methods of vegetative propagation may be used to multiply 



Bureau of Agriculture, P.I. 



Fig. 176. Varieties of lima beans, showing differences in size, shape, and color. 



