New YorkK AGRICULTURAL EXPERIMENT STATION. 345 
1.28 in the winter time. This solution is comparatively expen- 
sive and does not entirely separate the heaviest seeds, some of 
which are among the most common. Sodium nitrate holds up 
to about 1.39 in the warmest summer weather and to about 1.86 
in the winter time. This solution can be used for completely 
separating the heaviest seeds, such as Leguminosz and some of 
the cereals. 
The technique of solutions has not been much studied by the 
present writer and practically no attempt has been made as yet to 
use solutions of a density less than that of water. It is suggested 
however, that petroleum, naptha, benzine, etc., might be adapted 
to this purpose, if there was occasion for it. As a matter of fact, 
however, many seeds with a density as low as that of pure water 
do not germinate anyway and there is no need of carrying the 
separation below unity. The present writer has grouped all seeds 
of a specific gravity less than that of water together and indi- 
cated them collectively by the sign <1.00. The sign > is used 
_ to indicate “greater than.” 
DETAILS OF MANIPULATION. 
In practice, the solutions were made up in glass jars, deter- 
mining densities with a common dairy hydrometer. A part of the 
solution in each jar was poured into a saucer beside it, and the 
seeds to be separated poured into one of the higher solutions— 
which must be denser than any of the seeds—and all seeds that 
floated skimmed over with a piece of wire gause into the solution 
next lower. In each solution such seeds will settle as are denser 
than that solution but less dense than the one next above. 
In practice much difficulty is found in getting rid of adhering 
air bubbles. This difficulty can be obviated at least in part by 
dipping the seeds from water into some solution or into alcohol, 
formalin or some similar substance and then dipping them quickly 
back into: water. 
DETERMINATIONS BY PREVIOUS INVESTIGATORS. 
Mention should be made of some of the results obtained by 
previous investigators of the specific gravity of seeds. Nobbe 
gives a long table of specific gravities as reported by earlier 
investigators. Many of these determinations were made by Renz, 
