112 BREEDING CROP PLANTS 



variety test. If its value is unknown it is handled in the plant- 

 breeding nursery. The three groups, introductions, selections, 

 and crosses, are given nursery class and stock numbers for means 

 of identification. The year of the first test in Minnesota is also 

 carried (except in the case of crosses where the year that the 

 cross was made is used) , together with a series number from 1 

 to as many forms as are handled in the class for the year and 

 crop concerned. The following classes are used with the sup- 

 position that the forms were first tested in the nursery in 1920: 



Class 1-20-1, 1-20-2, etc Selections. 



Class II-20-1, II-20-2, etc Crosses. 



Class III-20-1, III-20-2, etc New Introductions. 



Supposing for example 20 new wheat introductions were grown, 

 these would be classed as III-20-1 to 111-20-20. All individual 

 plant selections are placed in class I if they are made from com- 

 mercial varieties or new introductions. The year that they are 

 first placed in the nursery is also carried, as well as the series 

 number. These class and series numbers are not changed as 

 long as the form is continued in the nursery trial. 



Crosses are not given a series number until the strain gives 

 evidence that it is homozygous. For the first few years the 

 method of numbering used by the United States Department of 

 Agriculture is followed. Thus a cross made between 1-14-1 and 

 1-14-20 is labeled at the time of crossing 1-14-1 X 1-14-20. 

 The female parent is written first. On growing this cross 

 in FI a convenient number or letter is used. Later generations 

 for the letter method would appear as A for F\, A-l for F z , 

 A-l-1 to A-l-200 if 200 plant selections were grown in F 3 . 

 As soon as a cross is purified, that is, when particular selections 

 appear homozygous, they are placed in the rod-row test and given 

 a series number; thus the cross made in 1918 would be labeled as 

 follows: 



First year, Class 11-18, A 



Second year, 11-18, A-l 



Third year, 11-18, A-l-1 to A-l-200 



Suppose A-l-10 and A-l-50 appear homozygous and look 

 promising, they would be placed in the rod-row test and receive 

 series numbers as II-18-1 and II-18-2. 



Bank figuring books have been found to be quite satisfactory 



