726 IOWA DEPARTMENT OF AGRICULTURE 



smooth and shining. Part of the seed of foxtail millet, Japanese millet, 

 and the foxtail weeds differs structurally from the last only in being 

 covered by two or three additional chaffy scales, which constitute the 

 "outer chaff." 



These features of form and structure are easily recognized when rep- 

 resentative seeds come to be compared under a magnifier, and it is ad- 

 visable to understand them in making tests of plover and grass seeds, 

 because the element of certainty is essential to satisfactory results. 



IMPURITIES OF FARM SEEDS. 



CLASSIFICATION. 



The impurities carried by farm seeds have an important bearing on 

 the real quality of the seed. Their quantity may be sufficient to unduly 

 increase the cost of the good seed and their character may be that 

 of injurious weeds. 



Seed impurities are classified (1) as inert material and (2) as foreign 

 seed, including both other crop seed and weed seeds. 



INERT MATERIAL. 



The inert material constitutes essentially such impurities as will 

 not grow (exclusive of dead seed), as chaff, empty seed hulls, broken 

 seed, pieces of stems and leaves, sand, dust, etc. The chief objection to 

 such material is that it replaces good seed, thus increasing the cost. In 

 grass seed the inert chaff misleads by causing the seed to present a better 

 appearance than its quality justifies, as in bluegrass seed and chaff redtop 

 seed. As compared with weed seeds, inert material is of minor import- 

 ance, a fact not to be overlooked in the purchase and use of seed. The 

 practical seed test should point out clearly the relative importance of 

 the inert matter and of the weed seeds found in the sample. 



OTHER CROP SEEDS. 



Seed of various farm crops sometimes constitutes a part of the foreign 

 seed. Its proportion as compared with the weed seed should be noted 

 in making the purity test. The importance to be attached to the occur- 

 rence of such crop seed depends on its nature; for illustration, the pres- 

 ence of timothy seed is detrimental to alsike clover seed used with a view 

 to alske seed production, while for hay production a mixture of timothy 

 and alsike seed often is preferable. 



WEED-SEED IMPURITIES. 



Quality and Kinds of Weed Seeds — Very few samples of forage-crop 

 seeds are found wholly free from weed seeds. The methods of culture 

 and of harvesting in vogue operate against a pure seed crop. The propor- 

 tion of the weed seeds appearing incidentally in the marketed seed is 

 dependent on the number and character of the weeds in the seed-producing 

 crop and the extent to which the seed has been cleaned before being mar- 

 keted. 



