140 Bulletin 251. 



progeny of the other only a few of the plants may show in any noticeable 

 degree the inheritance of the (juality. To determine this prepotency or 

 transmitting power, it is necessary to carefully grade the progeny of each 

 individual, and this is the primary reason for planting the progeny of 

 difTf.erent individuals in separate rows or separate plots, 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 plots by themselves to 

 get the comparative yield, for instance, of 100 plants, and from this 

 figure up the average per cent of the transmitting, or centgener power. 

 This matter, however, is very difficult in many cases. In corn, for 

 instance, certain individuals may stcol and form suckers that have 

 fairly good sized ears. If the corn is planted thin enough on the ground, 

 these suckers would tend to increase the yield, and render the proper 

 judgment of the transmitting power very difficult. It would seem at 

 first thought that such suckering, if it increased the yield would be de- 

 sirable, and should be considered a favorable character in connection with 

 an individual. However, if the soil is heavy enough to have allowed 

 this suckering to give increased yield, it would have been possible on 

 the same soil to have placed the plants closer, and as seed is of little 

 comparative value, it would be best to have a non-suckering type, and 

 plant the corn as closely as the soil would properly permit. Again, it is 

 almost impossible to get perfect stands, and a change in the stand may 

 affect the yield. A^ery many difficulties and problems enter into the figuring 

 out of this transmitting power, and it is obviously impossible to give 

 directions for all cases. The breeder must study conditions and carefully 

 determine what policy to pursue in each case. 



Control of /parentage. 



In plant-breeding, as in animal breeding, the isolation of the parents 

 is a very important consideration. It is necessary that we should know 

 the character of both i)arents wherever this is possible. In breeding 

 plants more attention is ordinarily given to the mother plant, and 

 in very many instances the characters of the father plant are entirely 

 neglected. Animal-breeders, on the contrary, give more attention to 

 the characters of the male parent, and a great deal of iiuprovement in 

 ordinary herds is accomplished by the introduction of improved blood 

 through the male. In ])lant-breeding it is desirable that the seed of the 

 select individuals be planted in a field by themselves. This insures that 

 only progeny of carefully selected plants will be planted near together, 

 and thus no ordinary stock will enter in as a contamination. One can 

 be certain that each ])lant of the progeny is fertilized with pollen from 

 another similarly good plant, or at least from a plant derived from good 

 parentage. One difficulty, however, has been experienced by plant- 



