PRINCIPLES OF SEED TESTING 367 



spread over a short period from the day the first 

 sprouting is observed. 



Care must be taken that the " seed-bed " (blotting- 

 paper or flannel) is kept moist, and each species should 

 be allowed the times mentioned at p. 371 in which to 

 germinate. The seeds which germinate strongly may 

 be removed from day to day and the number noted. 

 The average of not less than two separate lots of seed 

 should be obtained. The germinating capacities to be 

 expected from good samples of farm seeds are given at 



P- 37 1 - 



True Value of Seed. It is clear that if the sample 

 under consideration is very impure the germinating 

 capacity alone may give but a very inadequate idea of 

 the value of the seed. It is therefore necessary to 

 consider the two points together, and ascertain the 

 combined percentage value of purity and germinating 

 capacity. This may be done as follows : Suppose P 

 is the percentage of purity, G the germinating capacity, 

 and T the true or real value of the seed. Then 



PxG_ T 



IOO 



For example, if the purity be 95 per cent and the 

 germinating capacity 80 per cent, then we have 



IOO 



In other words, such a sample would contain no more 

 than 76 Ib. of good seed in every 100 Ib. purchased ; 

 or, to put it another way, there will be a loss of 243. 

 on every .5 worth of seed. At the same time, if the 

 5 per cent of impurity consists of weed seeds, great 

 trouble may be entailed by using the seed on the 

 farm. 



