COMPARISON OF SEED TESTING IN SAND AND IN THE 

 JACOBSEN GERMINATOR 



By J. A. Larse^n 

 Forest Examiner, Priest River Experiment Station 



The prevailing method of testing seed at Forest Service Experiment 

 Stations is by germination in sand. The advocates of the sand method 

 maintain that tests so conducted come nearest to the conditions which 

 naturally obtain in the nursery and field ; that the amount of moisture, 

 heat, and other physical factors affecting seed germination are more 

 easily controlled ; that this is the surest way to prevent damage by 

 fungi, and that the tests in sand need less attention and care than tests 

 conducted in any other media. 



If the accuracy of the tests and the application of the results hinge 

 so much upon testing and sowing in the same medium, we should ex- 

 pect to see soil taken from each individual seed bed for the testing of 

 the seed intended for those beds. To do this it would be necessary to 

 prepare seed beds in the fall in order to get a representative sample; 

 but this is not practical, especially where the testing is carried on some 

 distance from the nursery. Even if some investigators, actuated by an 

 unshakable belief in the efficacy of this method, should insist on it for 

 absolute results in a close study of comparative germination in the 

 greenhouse and the nursery, their results would only be of local appli- 

 cation and would have little value for field sowing. 



The supporters of the sand method have also overlooked the fact 

 that natural conditions do not occur in the sand tests. It would be im- 

 possible to duplicate the outside air temperature, soil moisture, air cir- 

 culation, etc., in a greenhouse. The only thing which could be consid- 

 ered identical is the sand or soil, and that of all the factors is the least 

 important in germination, and even this undergoes changes by leaching 

 during the progress of the tests. 



After several years of testing, the writer has found it very difficult to 

 control the factors of heat, moisture, etc., for the sand tests so as to 

 eliminate all variables. This is easily explained, since in order to have 

 standard conditions the trays containing the sand must have the same 

 size and shape, the sand must be taken from the same stratum from year 

 690 



