SELECTION OF SEED; FARM CROPS. 125 



into a colder climate. In other words, in changing 

 seed, particularly of the cereals, they should be secured 

 from the North rather than from the South. These are, 

 however, general suggestions, to be used as guides rather 

 than as specific and definite rules. 



Seed-Testing. The number of pure seed and the 

 germinating power are the two factors which determine 

 the number of plants that may be obtained from a given 

 quantity, rather than the bushels of seed sown. Seed- 

 testing includes, therefore, a test of purity and of ger- 

 minating power. 



Purity. The purity may be tested by taking a def- 

 inite weight to represent the product, and separating the 

 foreign matter, either by hand or by means of a sieve, 

 then weighing the remainder of pure seed. For example : 



Total weight taken . 100 grains or grams. 

 Weight of pure seed . 95 " " 



Weight of impurities 5 " " 



The amount of pure seed is, therefore, 95 per cent, 

 while the amount of impurities is 5 per cent. 



It is better in stating the impurity, consisting of for- 

 eign seeds, weed-seeds, etc., to use the number of seed in- 

 stead of their weight, as it gives a better idea of the 

 possible damage from its seeding. 



Germinating Power. In testing the germinating 

 power, only the seed true to kind are tested ; hence, a 

 high germinating power is not in itself sufficient evi- 

 dence of quality. It must be accompanied by a statement 

 as to purity; for instance, if the germinating power is 

 ninety per cent, and the purity only twenty-five per cent, 



