PLANT-BREEDING METHODS 433 



who advocates the organization of a recognized board of review which 

 will decide after trial and comparison, whether a submitted sample is 

 worthy of standing as a new variety or simply as a strain or stock. 

 Myers has conducted extensive strain tests of tomatoes and has 

 reached the conclusion that the best way to insure success in procuring high 

 yielding strains of vegetables is to secure seed a year in advance of the 

 time it will be needed and submit it to a preliminary test. The difficul- 

 ties encountered in selecting the most profitable strains within a variety 

 involve the same sources of experimental error as are met in variety 

 testing. The necessity of distinguishing between heritable and non- 

 heritable variations calls for individual plant selection and pedigree 



Fio. 180. Increase plots of one-thirtieth acre each. Selected strains of wheat from 

 the nursery are tested in these plots for 3 years. (After Montgomery.) 



culture methods. Plant-to-row tests and subsequent plot tests of the 

 progeny of individual wheat plants are shown in Figs. 178-181. In all 

 such work the use of loose leaf record blanks is advantageous. Two 

 forms of blanks used in testing pure line selections of oats are shown in 

 Figs. 182 and 183. Plant-to-row strain tests are still generally used 

 with cotton, corn and other cross-fertilized plants, but Hartley has 

 pointed out the importance of reducing experimental error to a minimum 

 in testing corn. 



Factors That Affect Experimental Results. In discussing the 

 standardization of field experimental methods Piper prepared the fol- 

 lowing list of factors affecting experimental field work with plants, 

 advising that they be published in connection with any series of field 

 experiments where relative yield is the object sought. 



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