ch. ix] Valuation and Purchase of Grass Seeds 163 



1. Genuineness. Cases of entire substitution of an inferior 

 or lower-priced species do not as a rule occur at the present time. 

 Nevertheless whenever the supply of seed of a particular species 

 falls short of the demand, as is frequently the case, there is always 

 the liability of an inferior allied species being substituted for the 

 required article. 



Thus Poa compressa may be sold as Poa pratensis, or Poa flava 

 as Poa nernoralis, etc. In all cases of doubt some of the seed 

 should be sent to a reputable seed-testing station. 



2. Purity. All foreign matter present may be grouped under 

 two heads : (a) adulterants, and (b) impurities. 



By the term adulterant is meant any ingredient which has been 

 intentionally mixed with the pure seed. Seed which is scarce or 

 high-priced is more liable to adulteration than cheap seed, e.g. Aira 

 flexuosa may be introduced into bulks of Avena flavescens, or 

 Poa pratensis into Poa nernoralis, etc. Again, a cheaper and 

 heavier seed may be introduced to increase the bushel weight of 

 another species. On the whole however it must be said in fairness 

 to the seed trade that wilful adulteration is a thing of the past, 

 and the above points are only mentioned here that purchasers 

 may be prepared for any isolated case of ignorance or fraud with 

 which they may be troubled. 



Impurities are ingredients which either occur naturally, or get 

 into the pure seed more or less by accident, and in many cases 

 cannot be entirely separated from it. They consist of : 



(a) Chaffy material, sand, earth, etc. 



(b) Seed of other cultivated plants. 



(c) Weed seed. 



It is of importance to note that the value of a sample is often 

 more affected by the nature of the impurities than by their actual 

 proportion in the sample 1 . A mere statement that a sample 

 contains say 90 per cent, of pure seed is of little value apart from 

 a knowledge of what the impurities consist. A certain pro- 

 portion of chaff is almost always present, and as a matter of fact 

 this must be the case with certain species in which some of the 

 chaff is adherent to the well-filled seeds, e.g. in Cock's-foot. Such 

 non-living impurities only reduce the value of a sample by replacing 



1 See Bibliography, No. 2. 



11—2 



