130 THE CORNELL READING-COURSES 



probably because the sexes are less clearly differentiated to the casual 

 observer. Until recent years, plant-breeding had not been dignified as a 

 subject for scientific study. Such investigation has shown that the same 

 principles of evolution and heredity apply to both plants and animals, 

 and that " good blood " tells in corn as well as in cows. At the present 

 time the breeding of plants is being presented in some fifteen institutions, 

 and definite instruction is received by one thousand to fifteen hundred 

 students. 



Every organism is the product of two factors, environment and heredity. 

 Environment means home conditions or surroundings. In the case of 

 plants, this includes soil, climate, and care. Heredity means the trans- 

 mission of similar characters from one generation to another. It is only 

 by giving attention to both these factors that the maximum yield of 

 crops can be produced. The environment must be good, that is, the soil 

 must be kept in good condition by fertilization and cultivation. It is 

 not the purpose of this pamphlet, however, to discuss that part of the 

 question, but rather to emphasize the factor of heredity. 



A great demand for conservation of resources has been sweeping over 

 the country during the past decade. At first the conservation movement 

 dealt mainly with the forests and the water power. Recently it has included 

 the conservation of the soil and mineral resources. The writer believes 

 that this movement should be further enlarged to include the conserva- 

 tion and propagation of high-yielding strains of plants. 



Many may think that the breeding of plants is a complex task, as com- 

 pared with the breeding of animals. This is not true. The laws and 

 principles that apply to animal-breeding apply also to plant-breeding, and 

 one who understands the breeding of stock should be able to apply this 

 knowledge to the improvement of plants. 



The plant-breeder has several advantages over the animal-breeder. 

 In the first place, he can handle -much larger numbers. He is able to 

 discard undesirable types of plants more easily than the stock-breeder 

 can discard " scrub " animals. In crossing, he can control the matings 

 more closely. 



METHODS OF BREEDING 



There are two general methods used in the breeding of plants: first, 

 hybridization, and second, straight selection. It is sometimes difficult 

 to separate these two processes, for selection is practiced to isolate and 

 preserve both forms already existing and those that may be produced by 

 hybridization. Sometimes the terms breeding and selection are con- 

 sidered to imply two different processes, but selection is merely one of the 

 methods of breeding. 



