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 
