RESEARCH SEMINAR. 245 



plant changed into a condition of variability, a condition which 

 would appear comparable to the mutation period predicated by 

 De Vries. The evidence in favor of the theory of breaking the 

 type is slight being based mainly on the experiments of Knight 

 and H. Vilmorin. 



July 28. The Principles of Selection and Isolation in Improv- 

 ing Varieties. By HERBERT J. WEBBER. 



This lecture described in detail the methods of selection used 

 in originating new races and strains of wheat, corn, cotton, sugar, 

 beets, and other agricultural crops. The nursery method of 

 planting introduced by Hallett and used extensively in this coun- 

 try by Professor Hays and others was compared with the field 

 method of selection introduced by Rimpau, and illustrations were 

 given of the use of each method in the production of new forms. 

 The nursery method gives to each plant all the space it requires 

 and allows the plant to show what it will do under the most 

 favorable conditions. The field method provides for the growing 

 of the plants under the conditions of field culture where different 

 individuals compete with each other in a struggle for existence, 

 the same as occurs in the ordinary conditions of culture under 

 which the plant is grown. 



The importance of considering the individual as the unit of 

 selection under ordinary conditions was emphasized but it was 

 pointed out that in some cases the selection of a fraction of an 

 individual will give quicker results. In corn for instance, the 

 kernels on an ear may show several different colors and it was 

 demonstrated that a uniform color can be secured more quickly 

 by separating out these kernels which show the desired color. 

 In hybrids of smooth and fuzzy-seeded cottons on the same 

 plant, some bolls may have nearly smooth seeds, while others 

 have fuzzy seeds in various degrees. It has been found that the 

 seeds in a single boll run very uniform either smooth or fuzzy, 

 and the evidence obtained on this point indicates that a larger 

 percentage of individuals producing smooth seed can be obtained 

 by selecting seed only from bolls producing smooth seed. These 

 points were emphasized to show that breeders must be prepared 

 to take advantage of every important point that may appear. 



