202 DOMESTICATED ANIMALS AND PLANTS 



patiently by dealing with relatively large numbers, always 

 remembering that recessives when evident are always pure, at 

 least as far as their own dominants are concerned. 



Systems of planting. In order to make safe and certain 

 progress in improvement of plants, definite systems of planting 

 must be observed. Two systems are in vogue, — the plot system 

 and the row system. Each has its advocates, and each has its 

 advantages for certain purposes. 



The plot system is the older. In this system the seeds of a 

 given selection are planted together in a small plot of ground, 

 which is labeled and numbered. In the row system each selec- 

 tion is planted in a separate row, which is also labeled and 

 numbered. 



Whichever system is adopted, adequate methods of number- 

 ing and recording not only the ancestry of the planting but also 

 the progeny or crop must be devised and rigidly adhered to ; 

 indeed, much of the success of improvement in plants, which 

 necessarily run into large numbers, is dependent upon the skill 

 and faithfulness of the record keeper. 



Records. The exact form of the record will of course depend 

 upon the particular plants and characters involved, and to some 

 extent upon the system of planting adopted, whether in plots 

 or in rows. For simple operations the student can devise his 

 own system of records, and for more complicated cases he is 

 referred to " Principles of Breeding," pp. 644-650, where com- 

 plete illustrations are given of the method of record keeping in 

 the wheat-breeding experiments at Minnesota, where the plot 

 system is used, and in the corn-breeding work at Illinois, where 

 the row system is in use. 



The general principle is that every plot or row be designated 

 by number, that every seed selection have also its serial number, 

 and that full descriptions be recorded of all plantings. A little 



that some of the Jersey and some of the Holstein-Friesian characters would 

 blend, making anything like a pure Jersey or Holstein-Friesian forever after- 

 ward impossible. 



