Seeds for the Garden 119 



have pollen parents that are quite worthless. Because 

 of this fact it is important in seed growing to make sure 

 that both parents are good plants. 



How new varieties are developed under cultivation. 

 Occasionally plants that are different from the others 

 appear in a crop, giving for example such differences as 

 are shown in the illustration on page 127. Sometimes 

 the difference is due to a natural variation. The new 

 kind of plant simply appears ; no one knows the cause 

 of the change in it. Such plants are called sports, or 

 mutants. 



In other cases new plant forms appear because pollen 

 from one kind of plant reaches the pistil and leads to 

 the fertilization of an egg cell of a different kind ; then 

 when the seed grows, it produces a plant that may be 

 different from either of its parents. Such plants are 

 called hybrids. Gardeners and plant breeders often 

 cross plants to combine the good qualities of both parents 

 in one plant and to cause to appear new qualities that 

 neither parents have. 



New varieties are developed from the seeds of these 

 new kinds of plants. All the different kinds of corn are 

 supposed to have come from one ancestor (which 

 may have been a hybrid). Possibly many of the 

 varieties were produced by saving seeds from plants 

 that were different from their parents. In the same 

 way all the different kinds of kidney beans, musk- 

 melons, and tomatoes have been developed by selecting 

 seed from plants that differed from their sister plants. 



The various members of the cabbage group illustrate 

 well how gardeners have developed from a common stock 



