THE WEIGHT AlTD GEEMHTATION TESTS. 



147 



the preliminary examination of a given lot of seed, so that the use- 

 less lahour of subjecting really bad seed to the more rigorous, hut 

 generally tedious, germination test may thereby be avoided. 



B. The Weight Test. 



In this test a suflSciently large measure or number of seeds is 

 •weighed and their average weight compared with the previously 

 ascertained standard weight of good seed. Seeds that are just 

 heavier than water, are sometimes tested by throwing them into 

 that liquid, those which float being obviously bad. 



This is a very uncertain method, for in the first place seeds of one 

 and the same species will have a different average weight in differ- 

 ent localities ; in the second place, seeds may lose an appreciable 

 part of their natural moisture, and hence also weight, without their 

 germinative power being at all impaired thereby ; and, in the third 

 place, the dealer or contractor might moisten the seed just before the 

 test. In any case, it ought never to be employed alone, but mere- 

 ly as an adjunct or auxiliary to the preceding or following method. 



C. The Germination Test. 

 In this system a given number of seeds, taken without selection 

 from a lot to be tested, is placed under the most favourable condi- 

 tions for germination, and then the proportion of seeds that actually 

 germinate, combined with the average time in which they have 

 germinated, is taken to indicate the quahty of the entire lot. The 

 quality will be directly as the proportion germinating and inversely 

 as the average number of days taken in germinating ; so that, ex- 

 pressed in figures, it may be represented by a fraction the numera- 

 tor of which is the percentage of successful seeds and the denomi- 

 nator the average number of days taken by each successful seed to 

 germinate. We wiU explain this by an example. Suppose that 

 200 seeds are sown and germinate as follows: — 

 total number of days = 



J.C. 140 in all have germinated in a total number of 1064 days, 



