COMPARISON OF SEED TESTING 695 



in ordinary seed testing. The tests may be completed in much less 

 time ; an expensive greenhouse and high costs for fuel are avoided, 

 since a germinator large enough for from ten to fifteen duplicate tests 

 can be made for about $25, and it can be used in any laboratory, office, 

 or kitchen and be heated by means of gas, electricity, oil, or alcohol. 



This germinator is most suited for use with the more rapidly germi- 

 nating species, and for these the differences in rate of germination and 

 the time required is most pronounced. It may, however, be used to 

 good advantage with the slower species, as Pinus strobus, Pinus monti- 

 cola, and the species of Abies, provided a satisfactory pre-germination 

 treatment has been discovered. In the above tests Pinus monticola seed 

 was treated by mixing with moist, bark-free sawdust for six weeks. 



It is a matter of great importance in seed testing to uncover the rea- 

 son for the more rapid germination by the Jacobsen method. It is not 

 due to heat alone, because the temperature rose higher in sand and 

 maintained a similar fluctuation and average. The moisture conditions 

 surrounding the seed are much more uniform in the germinator, but 

 only a small part of each seed touches the wet filter paper, leaving the 

 rest of the seed exposed to a moist-air medium, while the seed in the 

 sand is in contact with the sand particles, and most of the moisture 

 made available for the seed is in the form of capillary water. The 

 results of these tests, as well as germination in sand of the same species 

 of seed under different conditions of air moisture, during which better 

 germination took place under increased moisture, lead to the supposi- 

 tion that germination is hastened more by water vapor than by moisture 

 in a liquid state. It is probable that the greater heat energy in moist 

 air as compared with dry air causes the more rapid germination, for it 

 is an established scientific fact that under a given pressure of 760 milli- 

 meters and a temperature of 50 degrees Fahrenheit one kilogram of 

 saturated air, then containing 7.5 grams in the form of vapor, possesses 

 as much heat energy as dry air at 84 degrees Fahrenheit.- This brings 

 us face to face with a new factor which may prove of great imi>ortance 

 in seed studies and which offers an interesting field for future investi- 

 gations. 



' Der Warmeaustauch in festen Erdhoden in Gewiissern und in der .\tmosphare. 

 Julius Springer, Berlin, 1904. 



