342 TWENTY-FIFTH ANNIVERSARY REPORT. 
maturing process in the seed will continue so long as the seed is on 
the plant even though the plant itself be removed from the soil. 
The last phase of seed investigation carried out by this Station 
was “ Seed Selection According to Specific Gravity.’’*> ‘The specific 
gravities were determined by the use of salt solutions of various 
strengths, the seeds being immersed in the salt solution and those 
rising to the surface being skimmed off, while those which sank 
were placed in a stronger salt solution. This method of deter- 
mining specific gravity is, we are informed by the investigator, an 
old one used by gardeners in China and Japan for 250 years. 
Previous investigations have presented very contradictory verdicts 
as to the effect of this method of seed selection upon the resulting 
crop. As the results of the investigation here were different for 
almost every kind of seed used it does not seem strange that this 
should have been the case. As was shown in earlier investigations 
at this Station, and has been demonstrated elsewhere, with some 
plants heavier seeds will produce more vigorous seedlings than 
those of lighter weight. 
The writer thinks it possible that in many instances the grading 
of seed according to specific gravity is practically the same as 
grading according to weight; that is, the heavier seeds have the 
greater specific gravity and the lighter seeds the lesser specific 
gravity, so that the results might be wrongly credited to a greater 
specific gravity rather than to a greater weight of seed where these 
characters appear together. 
Seeds of the following plants were tested: Mustard, timothy, 
clover, peas, carrot, turnip, cauliflower, cabbage, egg-plant and 
pepper. 
In the case of the mustard it was found that the specific gravity 
varied from 1.01 to 1.21 with the most of the seed ranging on 
either side of 1.15. The earlier and apparently stronger germi- 
nations ranged from 1.12 to 1.19. The seeds of neither very light 
specific gravity nor very heavy specific gravity gave as good germi- 
nations as those of medium specific gravity. In the case of timothy, 
the seed of which ranged from 1 to 1.26, the best seed appar- 
ently in every respect was that of the heavier specific gravity, the 
percentage of germinations being greater and the plants more 
vigoreus. Clover ranged generally from less than 1.17 to above 
1.30, and seeds of medium specific gravity gave the best results, 
those from 1.23 to 1.26 being the best of the lot. Champion of 
* Bul. 256; also in Ann. Rpt. 23:335, 1904 
