ELEVENTH ANNUAL YEAR BOOK— PART XI 743 



The pure seed. After the sample is weighed it is spread on a sheet 

 of white paper folded in the form of a tray and should first be examined 

 with reference to whether it is true to name. Attention should then 

 be directed to the possible presence of some particular adulterant 

 liable to be present. All the foreign seeds (except certain adulterants), 

 including other crop seeds and weed seeds, also inert matter, as pieces 

 of steins, chaff, sand, and badly broken seeds, are to be separated from 

 the kind under test. Both plump and shriveled crop seed should be 

 classed as "pure seed." While the shriveled seed very evidently may be 

 worthless it nevertheless is a part of the crop seed, and its worthlessness 

 will appear in the subsequent germination test. 



If certain specific adulterants, as trefoil, sweet clover, bur clover, Can- 

 ada blue-grass, and rye-grass, are found, the adulterant seeds are left 

 mixed with the crop seed when the other foreign seeds are separated. The 

 proportion of the adulterant is then determined by count from a part of 

 the mixture. 



If certain kinds of foreign crop seeds or of weed seeds are especially 

 abundant it may be desirable to keep them separate from the rest in 

 order to determine their quantity, but if not the foreign matter for con- 

 venience may be mixed together irrespective of its character. In official 

 tests the foreign seed and the inert matter are separated, their quan- 

 tities being determined individually. After the pure seed and the foreign 

 materials of the sample have been separated the proportion of pure seed 

 is determined by comparing its weight with that of the entire sample, ex- 

 pressing the result in per cent. If quantities of seed weighing (jY^ shots 

 or 12% shots have been taken for the original test sample, each 1-16 shot 

 weight of pure seed represents 1 per cent or one-half of 1 per cent, re- 

 spectively. 



Determination uf adulterants. — When an adulterant is found and its 

 kind ascertained by examination, its quantity must be determined. When 

 such seed as that of trefoil, sweet clover, Canada bluegrass, and other 

 kinds have been used, their separation from all the pure seed of a test 

 sample is laborious and not justified by the information gained. Since 

 the weight of these seeds is approximately the same as that of the seeds 

 with which they are mixed, their relative proportion to pure seed is de- 

 termined by count. After all other foreign seeds and other materials 

 have been separated from the pure seed and adulterant together 1,000 

 seeds of the mixed crop seed and adulterant are counted out indiscrim- 

 inately. This number of seeds is then carefully separated into pure-crop 

 seed and adulterant and the number of each ascertained by actual count. 

 If a sample of red clover seed is found to be adulterated with trefoil to 

 the extent of 400 seeds in 1,000 seeds of the mixture, the trefoil is de- 

 termined to be 400 divided by 1,000 equals 40 per cent of the mixture. 

 If other foreign matter in the sample amounts to 15 per cent, the clover 

 and trefoil mixture represents 85 per cent of the original sample. The 

 trefoil adulterant therefore amounts to 40 per cent of 85 per cent, or 34 

 per cent of the seed under test 



