TOG Report on Inspection Work of the 



sample. The sum of percentages of foul or foreign seed and of inert 

 matter was subtracted from one hundred and the result recorded as 

 the percentage of pure seed. 



In some cases the percentage of pure seed as determined by the 

 above method was somewhat lower than it would have been had 

 the percentage composition been found by weight. From studies 

 made upon the relationship between " weight " and " count ' ; 

 methods for determination of percentage of purity of seed it was 

 found that in every case where the seed was well cleaned with modern 

 cleaning machinery and the seed impurities were of about the same 

 size and weight as the crop seed, even if they represented several 

 species, the two methods agree closely. It was also found that the 

 lower the grade of seed and the less the amount of cleaning it had 

 received the smaller in size were some of the seed impurities and con- 

 sequently the higher was the percentage of impurity by count as 

 compared with the percentage of impurity by weight. The reverse 

 would be true if the crop seed was contaminated with a foreign seed 

 of much larger size and weight, as would be the case if timothy 

 seed was present in a sample of redtop seed. 



The analyses of several conspicuous samples may serve to illustrate 

 the foregoing statements: A sample of redtop seed contained 515 

 seeds of a species of rush (J uncus tenuis) which represented 4.53 

 per ct. by count of the total number of seeds in the sample, but 

 when weighed upon a delicate balance and the percentage recorded 

 by weight, these 515 seeds of rush, which are very small, showed a 

 percentage of only 0.5, a difference of over 4.0 per ct. The seeds of 

 this rush are, in many cases, stuck together in little bunches by a 

 mucilaginous substance, thereby making it very difficult to separate 

 them for the purpose of counting. In this case the mucilaginous 

 substance was dissolved with alcohol and xylol and the rush seeds 

 counted with the aid of a binocular microscope. 



A sample of alfalfa seed (No. 23), in which the seed impurities 

 consisted mainly of timothy, gave a percentage of 2.0 by weight, or 

 a percentage of 8.8 by count. This sample proved to be a violation 

 of the seed law when the purity percentage was determined by the 

 " count " method. 



A sample of alsike clover seed (No. 15), which was badly contami- 

 nated with timothy and weed seeds smaller in size than those of the 

 alsike clover, showed 9.5 per ct. foul or foreign seed by weight or 

 17.5 per ct. by count. 



