sEt;u TESTING 47 



impurities, each by itself. Then each lot is weighed and 

 the percentage of purity computed. From the pure lot 

 thus separated, 100 or 200 seeds are selected and placed 

 in a germinator so they do not touch each other. In due 

 time under favorable conditions, sprouting will follow 

 and the percentage of germination may be determined. 

 To calculate the true value of the seed, multiply the per- 

 centage of purity by the percentage of germination and 

 divide by 100. For instance, suppose a sample to be 90 

 per cent pure and have 80 per cent germination ; 

 90 X 85 -^- by 100 = 83.3 per cent. That is, 100 pounds 

 would contain 83.3 pounds of pure, germinable seed and 

 16.7 pounds of dead seeds, weed seeds, dirt, etc. "What 

 man in his right senses would pay for the latter? 



76. The longevity of seeds, the percentage of germina- 

 tion and the purity of the sample have much to do with 

 the resulting crop. In the table on page 49, the per- 

 centages of purity and germination (by Duvel) are high 

 averages in high-grade seed ; the figures (years) on 

 longevity are from Vilmorin. As an indication of the 

 importance of securing high-grade seed the following 

 instance speaks for itself. 



