Tolerance 



Owing- to the natural variation between tests, the following tolerances 

 shall be allowed between the percentages found by analysis, test or ex- 

 amination and the percentages stated on the tag accompanying the seed : 



For purity: Allowing- "a" to represent the component being con- 

 sidered and "b" the difference between that percentage and 100, according 

 to the following" formula : 



( a X b ) 



Pure seed tolerance=0.6+ ( 0.2 X ) 



( 100 ) 



a sample of timothy guaranteed 99.20% could test as low as 98.40% and 

 be "satisfactory." 



For germination : The following tolerances are applicable : 



Mean: Tolerance 



96 or over 5 



90 or over but less than 96 6 



80 or over but less than 90 7 



70 or over but less than 80 8 



60 or over but less than 70 9 



Less than 60 10 



Therefore, a sample of seed guaranteed 85% for germination may be as 

 low as 77% and be "satisfactory." 



For weed seeds : The law requires in the labeling of agricultural seed 

 (l)that the percentage of all v/eed seeds present shall be shown on the tag, 



(2) that no primary noxious weed seeds shall be present in the sample, and 



(3) that, if present, the names of the kinds of secondary noxious weed seed 

 and the rate of occurrence of each shall be stated: (A) Per ounce in 

 Agrostis spp., Poa spp., Rhodes grass, Bermuda grass, timothy, orchard 

 grass, fescues, alsike and white clover, reed canary grass, Dallis grass, rye- 

 gi^ass, foxtail millet, crimson clover, Brassica spp., flax, Agropyron spp., 

 and other agricultural seeds of similar size and weight, or mixtures within 

 this group, and 



(B) Per pound in proso, Sudan grass, wheat, oats, rye, barley, buck- 

 wheat, sorghums, vetches, and other agricultural seeds of a size and weight 

 similar to or greater than those within this group or any mixtures within 

 this gi'oup. 



Certain tolerances are allowed, however, to provide for variation and 

 unavoidable errors, but only within very narrow limits and for which there 

 is always a standard formula for computation. Examples: (1) Timothy 

 guaranteed only 2 per cent w^eed seeds will not be condemned if it has a 

 2.59 per cent. (2) No primary noxious weed seeds are allowed, but the 

 presence of two such seeds in 50 grams of timothy would not be considered 

 a violation. (3) Similarly, some slight variation from the minimum require- 

 ment for labeling secondary noxious weed seeds will be passed as satis- 

 factory. 



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