Methods in Germination Tests of Coniferous Tree Seeds 75 



another ; germinative energy is stated to be merely the % rapidity 

 of germination by one and held to be the force with which the 

 seed breaks through the soil by another. It can readily be seen 

 that some confusion exists. 



Since this time limit was established in order to arrive at a 

 closer index of the value of seed for field purposes and to secure 

 a greater economy in seed, I shall use the terms, "practical 

 germination period", instead of the American terms germinative 

 energy or germinative force period, and "practical germination 

 per cent" to replace germinative energy or germinative force, 

 and thus avoid any misunderstanding due to the present con- 

 fusion of terms. By practical germination per cent, I mean 

 the germination per cent at the end of a definite period, fixed 

 by the judgment of the investigator, after which seeds germinat- 

 ing are believed to produce seedlings valueless for field purposes. 

 The practical germination period must always be given with the 

 practical germination per cent in order to render the latter 

 figure of any value. Thus: Practical germination (30 days) 

 66 per cent. 



As I use practical germination per cent in this paper, two 

 seed samples of the same species and having the same practical 

 germination per cent for the same practical germination period 

 would be considered of equal value for field purposes which 

 would probably be true provided some form of filter paper 

 germination apparatus had been used in every case and the 

 practical germination period had been relatively short, for in- 

 stance, seven days. But this assumption should not be applied to 

 results obtained from germination tests in soil where the practical 

 germination period is so much longer, often from twenty to 

 thirty-five days, that there is every possibility of variation in 

 speed of germination within this practical germination period 

 for two seed samples with the same practical germination per 

 cent. For example, two samples of western yellow pine seed 

 with a practical germination of 40 per cent for a period of 25 

 days in soil test would be considered of equal value for field 

 or nursery sowing. But if one of these samples should show a 

 germination of 30 per cent in twenty days while the other had 

 a germination of only 25 per cent for the same period it is 

 obvious that the first sample is better than the second for 

 practical purposes. Careful attention, then, should be given to 

 the daily progress of germination within the practical germina- 

 tion period in deciding the relative merits of seed samples under 

 test. To simplify comparison, the daily germination should be 

 plotted as a curve using the per cent of germination as the 



