als A TEXT-BOOK OF BOTANY 
Among them there may be found one or more with a desired 
variation, or at least the beginnings of it. These plants are 
preserved and the others destroyed. Often many thousands 
of young plants are thus started, and most of them de- 
stroyed. = 
180. Selection.— When a desired variation has appeared, 
the work of improving and establishing it must follow. 
This is done by means of selection, and it involves great care 
and patience. The selected plants are carefully guarded, no 
foreign pollen being allowed access to their flowers. Their 
seeds are planted, and among the new plants that come up 
those showing the desired variation are preserved and the 
others are destroyed. This selection goes on generation 
after generation until only the desired variety is produced. 
It is then said to be established, and can usually be de- 
pended upon to produce its kind. 
Even after a variety has thus been established, great 
care must be used in selecting from the best plants seeds 
for planting, or the variety will “rundown.” It isa great 
mistake to suppose that seeds from inferior plants will do Just 
as well for sowing as seeds from the best plants. Farmers 
have learned this in selecting their seed-corn, seed-wheat, 
etc.; and their success depends upon their wise selection of 
the seeds to plant. It is important to know that in this 
selection of seed the character of the individual plant that 
produces it is the important thing. To select for planting 
the largest ears of corn from a pile of corn does not result so 
well as to sclect in the field the plants that produce on the 
average the best ears, 
The process of selection is being applied also in the 
development of varietics that resist certain diseases. For 
example, in a field that has been ravaged by some disease 
a few plants may be found that have resisted the attack 
successfully. This means that the variation in these plants 
is a very desirable disease-resisting power. Starting with 
