284 BREEDING CROP PLANTS 



METHODS OF SEED PRODUCTION 



After obtaining the better variety for the locality, the seed 

 grower has the problem of keeping this variety in the same high 

 state of production and if possible to improve it. The purpose 

 of this chapter is to outline methods for the various crops which 

 may be used by the seed grower or by the average farmer. 



Farm crops may be placed in four groups according to their 

 modes of reproduction. There is a close relation between this 

 characteristic and the farmer's methods of seed production. 

 The four groups mentioned are as follows: 



Group 1. Generally self-fertilized: Barley, wheat, oats, peas, beans, flax, 

 tobacco. / 



Group 2. Often cross-pollinated: Corn, rye, most grasses, root crops. 



Group 3. Cross-pollination obligatory: Red clover, sunflower. 



Group 4. Vegetatively propagated : Potatoes, sugar cane, sweet potatoes. 



Among farm crops, the production of seed generally depends 

 on a union of the male reproductive cell, contained in the pollen 

 grain, with the female reproductive cell the egg cell. 



The pollen grains of corn are produced in the tassel and each 

 thread of silk leads to an ovary which contains the egg cell. In 

 order to produce seed, the male reproductive cell must pass down 

 through the silk and unite with the female cell. This process is 

 called fertilization. If pollen and silk are borne by the same plant 

 the process is self-fertilization, and if by different plants, cross-fer- 

 tilization. As the egg cell and the pollen grain of self-fertilized 

 plants are, as a rule, alike in their inherited characteristics, the 

 progeny of a single self-fertilized plant, such as barley, wheat, or 

 oats, have the same inheritance. There is, of course, considerable 

 variation in all characters, owing to environmental effect, but all 

 evidence shows that these differences are not truly inherited. 

 Occasional crosses occur in self-fertilized crops which cause inher- 

 itable variability. Mass selection serves to eliminate these off 

 types. 



SEED GROWERS METHODS FOR SELF-FERTILIZED PLANTS 



For self-fertilized plants the grower can, as a rule, obtain a 

 pedigreed strain which is nearly adapted to his conditions. The 

 only thing that he can do with this variety is to save seed in such 

 a way that mixtures of other strains or occasional crosses are 

 eliminated, together with obnoxious weed seeds and diseases. 



