PURITY 617 



so far as the purchaser pays for what he does not require. If 

 the sample contains 6 per cent, of foreign matter in every 100 

 lbs., he pays for 6 lbs. of something which is not the true seed 

 he intends to use. In some instances this may not be of much 

 importance, for example, where one kind of grass seed is mixed 

 with another of equal value, both pecuniarily and from an 

 agricultural point of view. By far the larger number of im- 

 purities however are either useless, as husks, chaff, and bits of 

 straw and dirt, or worse than useless as in the case of weed seeds. 

 The latter point is worthy of greater attention than is usually 

 given to it by farmers, as a small percentage of deleterious seeds 

 often means a considerable number of weeds per acre. This is 

 most easily seen when we consider the grasses where the number 

 of seeds sown is usually very large. For example, 40 lbs. of 

 grass seeds sown for permanent pasture, will contain more than 

 15 million seeds capable of germination; if only i per cent, of 

 these is a weed, it means the possibility of between 30 and 40 

 such plants on each square yard of the ground. 



In examining samples, therefore, it is not merely necessary 

 to determine the amount of impurity present, but its nature is 

 of importance — whether it be inorganic, such as sand and dirt, 

 or organic material in the form of living seeds. The determina- 

 tion of the species of foreign seeds present in a sample requires, 

 in some cases, special care and experience but all the more 

 commonly occurring and easily recognised impurities will be 

 mentioned when dealing with the character of each variety of 

 seed separately. It is important to point out in this connection 

 that impurities may be natural, that is, the foreign seed present 

 may be there on account of the impossibility of ever obtaining 

 a perfectly clean piece of ground on which to grow the crop for 

 seed, or because of accidental mixing when the seeds are hand col- 

 lected, as in the case of certain grass seeds. There are, however, 

 samples met with in which the impurities present cannot well 

 be anything but definite adulterations — additions of seeds of 



