624 FARM ' SEEDS ' : GENERAL 



ture should be tolerably even, and in the more elaborate 

 apparatus used at seed testing stations these factors are under 

 control, and the results obtained are consequently more accurate. 

 Attention to the amount of moisture supplied to the seeds is 

 very important, and too much is often given by beginners. 

 Large seeds, such as beans, peas, and vetches, require con- 

 siderable amounts ; crucifers, cabbage, turnip, and mustard 

 much less, while least of all is needed by the grasses and 

 smaller seeds. Usually a steady temperature and even supply 

 of moisture are best for germination, but the seeds of mangels 

 and carrots and nearly all grasses are benefited by irregularities 

 as the embryos become free from their coats more quickly when 

 dryness and dampness succeed each other. Whether this is 

 due to mechanical splitting of the walls of the fruits or to some 

 influence upon the respiration and other physiological processes 

 of the seed is not certain. In laboratories where the tempera- 

 ture is under control, sixteen hours at i8° C. followed by eight 

 hours at 28° C. alternately, is found best for mangel seed. 



Every day during the time previously specified as necessary 

 for the test, the seeds which show active signs of life are counted 

 and removed. At the end of the trial the number of living 

 seeds compared with those which are inactive is known, and 

 from this the percentage or number of living seeds in every 100 

 can be calculated, and the germination capacity is usually stated 

 in this manner. For instance, in the sample of red clover 

 previously mentioned and examined for purity, out of every 

 250 separated true seeds 240 only were capable of growth ; the 



germination capacity was therefore ^4° x 10° ^ g ^^^^^ 



250 



From the result of the purity examination and that of the 



germination capacity taken together, the total percentage of 



living useful seeds in the ample as originally purchased can 



be calculated. The figures obtained, namely 97 per cent. 



purity and germination capacity of 96 per cent., mean that in 



