38 



Individuality in Plants. 



Substantive differences, on the other hand, are more subtle. In 

 individual plants these qualities cannot be measured, weighed, or 

 accurately determined. Knowledge of correlations may be of 

 service in helping- to arrive at a decision, but the ability of a plant 

 to transmit its characters must be the final test. The closest study 

 of the physical characters of a number of plants, with a view to 

 securing uniformity in general conformation, will come far short 

 of enabling the breeder to determine the projected efficiency of 

 the individuals under consideration. Such information can be 

 obtained only by testing separately the progeny of each plant 

 under conditions as nearly uniform as possible. 



For this purpose the centgener system was devised — a system 

 which renders possible the testing of a large number of mother 

 plants whereby a record of the performance of each plant is 

 obtained. The plant is the unit of selection. The centgener is a 

 trial plot of one hundred grains planted from the product of a 

 single mother. 



A prime requisite in planting a foundation bed from which 

 mothers are to be selected is to have all the plants grown under 

 •conditions as nearly the same as possible. To secure this equality 

 of opportunity, so far as external conditions can be controlled, 

 carefully chosen grains taken from hand-selected heads of the 

 most promising varieties are planted in foundation beds four inches 

 apart each way. The plants resulting from this seeding are pulled 

 and studied separately in the field at harvest time, and are sub- 

 sequently subjected to a more severe test in the laboratory. So 

 rigorous is this selection, based on the physical characters of the 

 plants, that not more than one in five hundred is considered 

 eligible for trial in the centgeners. The same fundamental tests 

 are applied to the centgeners as were applied the previous year 

 to the individual plants in the foundation beds. This reduces 

 the number eligible for registration to one in one thousand, and 

 frequently this proportion cannot be had. Full notes are taken on 

 the centgeners in the field, and the next season multiplying plots 

 are sown broadcast from those centgeners which have the best 

 performance record. In the fifth year the product of the multiply- 

 ing plots enters into competition with the original variety. If, in 

 this contest, it proves superior to the original stock it will be 

 multiplied on the general farm as rapidly as possible and sold to 

 the farmers at a reasonable price. 



In our work so far, numerous variations, some desirable and 

 many undesirable, have been isolated from the 550,000 plants 

 studied during the past three years. The progeny of many of 

 these mothers has differed widely from the parent plant and con- 

 sequently from each other ; the progeny of each mother from the 

 best plants has always been remarkably uniform within itself, and, 



