FIELD CROPS 373 



make a preliminary selection of a much larger number of plants 

 than are actually desired. The breeder can then examine these 

 selections with greater care and discard the poorest from among 

 them, retaining only the superior individuals. 



Careful breeders have found it very desirable to have a clearly 

 defined ideal type which they are striving to produce. In selections 

 within the race the breeder should have all of the characters of the 

 race which he is breeding clearly in mind in order to adhere strictly 

 to the type of the variety in the selections. In making selections 

 of new variations, mutations, etc., in attempting to secure new races, 

 naturally no one type can be adhered to. In testing these different 

 individuals, however, the characters of a certain type should be 

 borne in mind and deviations from this type in the progeny should 

 be weeded out. 



The unity of the individuals is also an important factor in 

 plant-breeding. If, for instance, one is attempting to produce a 

 seedless fruit, it is important that he discover a plant which shows 

 a tendency to produce seedlessness throughout the entire individual. 

 It would not be the correct policy for a breeder to select simply a 

 single fruit which might accidentally be nearly seedless. He should 

 examine a large number of fruits of different individual plants, and 

 find a plant on which he can discover a general tendency toward 

 seedlessness, showing in all of the fruits produced. By selecting 

 seed from such individuals he may be able to find in time one such 

 individual that will transmit to its progeny this tendency to 

 produce few seeds. 



A factor of primary importance in all breeding is the testing 

 of what is termed the transmitting power. It is necessary for us to 

 know that a certain plant, which for instance, gives a heavy yield, 

 has the faculty of transmitting this tendency of producing heavy 

 yield to its progeny. It is frequently found that two select plants 

 which are equally good so far as their yield is concerned will give 

 progeny which, as a whole, differ greatly in this respect. In the 

 progeny of one, almost every plant may have inherited the quality, 

 while in the progeny of the other only a few plants may show in 

 any noticeable degree the inheritance of the quality. To determine 

 this prepotency or transmitting power, it is necessary to carefully 

 grade the progeny of each individual, and this is the primary rea- 

 son for planting the progeny of different individuals in separate 

 rows or separate plats, so that they may be easily examined. It 

 would seem to be an easy matter when we plant the progeny of 

 different plants in rows or small plats by themselves to get the com- 

 parative yield, for instance, of from 25 to 100 plants, and from this 

 to figure up the average per cent of the transmitting power. 



Control of Parentage. In plant-breeding, as in animal-breed- 

 ing, the isolation of the parents is a very important consideration. 

 It is necessary that we should know the character of both parents 

 wherever this is possible. In breeding plants, most attention is ordi- 

 narily given to the mother plant, and in very many instances the 



