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has been produced. In such a selection the scientist would assume 

 that there had been no change produced in the type of the race but 

 that the breeder by the selection and isolation of the maximum 

 yielding individuals had produced a family, within the race, of 

 high yielding capacity, this being maintained continually by the 

 selection. If, however, the selection and isolation of the highest 

 yielding plants was discontinued and free intercrossing with inferior 

 individuals was allowed, the mean yielding capacity of the race as 

 a whole would soon be established again. 



The keynote of improvement by selection is the choice of the 

 very best individuals. The discovery of the best individual in any 

 crop under consideration, requires the growing of a large number 

 of individuals under as uniform conditions as possible, so that the 

 experimenter may have opportunity to examine and select the best. 

 Two methods of growing plants for selection are in general use 

 which may be termed 1, the Nursery method, and 2, the Field 

 method. The Nursery method consists in cultivating each plant 

 under the most favorable conditions possible for its best develop- 

 ment. By this method with wheat, for instance, Hallett pursued 

 the policy of planting the individuals in squares a foot apart, which 

 would give each plant abundant opportunity for stooling, and also 

 the investigator an opportunity to clearly distinguish each indi- 

 vidual plant and determine its characteristics, total yield, and the 

 like. In recent years this method of growing the individual plants 

 at a standard distance from each other in order to test their yielding 

 capacities, and the like, has been used by Professor Hays in his ex- 

 periments at the Minnesota Station. Here, however, a standard 

 distance of four inches apart was used instead of one foot. 



By the Field method the selections are made from plants grown 

 under normal field conditions. The claim for this method is that 

 we can only judge what a plant will do in the field under ordinary 

 conditions of field culture, by growing and selecting it under these 

 conditions. In the large majority of cases the first selections are 

 probably made from plants grown in the field in the regular course 

 of crop production, which thus were not specially grown for the 

 purpose. 



If one is to use the Nursery method, the plants must be espe- 

 cially planted. While the nursery method certainly allows the 

 breeder to distinguish the individual plants more clearly, in crops 

 like wheat, oats, and so on, which are sown broadcast or drilled, it 

 entails very much extra work and is probably to be recommended 

 only for the use of experimenters who are giving their entire time 

 to the work. 



In selecting the best plants in any crop the breeder must aim 

 to examine a very large number of plants and carefully compare 

 their important characters. To know what the important characters 

 are, it is necessary to be familiar with the crop and have a thorough 

 knowledge of those qualities which go to make up a plant of the 

 greatest intrinsic value. 



In making the first selections it is usually the best policy to 



