CHAPTER NIX 
PLANT BREEDING 
176. Definition.—The purpose of plant-brecding is to 
improve cultivated plants, Just as the purpose of animal- 
breeding is to improve domesticated animals. Great pro- 
gress has been made in the science of plant-breeding, so 
that it is possible now in many cases to breed for certain 
desired improvements with great confidence that they will 
be secured. The skilful plant-breeder not only must know 
how to make plants grow, but he must know also the laws 
connected with the reproduction of plants. 
177. Variation.—The fact with which the plant-breeder 
starts is that plants tend to vary. If all the seeds from one 
parent plant are sown, the plants that come from them 
will all resemble the parent in a general way; this handing 
down of similarities from one generation to the next is called 
heredity. But while there is this general resemblance to the 
parent, there ure variations, one or more of the new plants 
perhaps resembling the parent less than the others do. It 
is this fact that makes plant-breeding possible; and instead 
of relying upon nature to present to him all the variations 
he needs, the plant-lbreeder by changing conditions increases 
the tendency of plants to vary, and also by crossing multi- 
plies variations. The important thing is to obtain as many 
and as wide variations as possible. 
178. Vegetative propagation.—If among varying plants 
there appears one that is desirable, it may be possible to 
propagate it vegetatively, that is, without using the seed. 
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