New YorK AGRICULTURAL EXPERIMENT STATION. 383 
together, showing their equal density, and showing further that 
this dark covering (the inner seed-coat) is of much less density 
than the cotyledon itself, which is otherwise obvious. By the 
same method the difference in density between the cotyledon and 
the radicle can be shown. This method may also be used in some 
cases to locate quickly large air spaces if such exist in one part 
of a seed, as in the grape seed and sweet corn. In the latter case 
the air spaces are around the embryo. 
APPLICABILITY OF THE METHOD OF SEED SELECTION 
ACCORDING TO SPECIFIC GRAVITY. 
The method of separating seeds into a series of separates of 
approximately uniform densities is of course a method of inves- 
tigation and not of practice. By means of it, together with cul- 
ture tests, may be ascertained the limits of specific gravity with- 
in which the most desirable seeds for planting are embraced. 
The practical application of the method consists in making up 
one or two solutions of predetermined densities and by means of 
them separating the seeds that are to be planted. 
The method of solutions is of only restricted application, but 
within limits it appears to give promise of considerable useful- 
ness. Specific gravity is of not nearly so great moment in seed 
selection as is size; but after seeds have been separated into 
lots of approximately the same size by sifting, then the method 
of specific gravity carries the selection a step farther. The most 
desirable method of selecting seeds would be to weigh each indi- 
vidual seed; but this is out of the question in field practice. 
If seeds were of uniform density, the method of sifting should 
alone admit of selecting the desirable individuals; but the size 
does not take into account the density of the seed. These two 
methods of selection are combined in the fanning-mill method and 
in the method of seed selection by means of centrifugal force; 
but on the other hand, neither of these methods admits of exact- 
ness of application as does the method of solutions. 
Some kinds of seeds do not admit of sifting satisfactorily on 
account of either small size or irregular shape. To this category 
belong timothy seed, carrot, tomato, egg-plant and pepper. To 
such seeds the method of solutions is especially applicable, since 
