384  ReporT OF THE HORTICULTURAL DEPARTMENT OF THE 
various other physical properties of cultural importance are cor- 
related with specific gravity. 
The method of solutions is rather unsatisfactory of application 
to seeds such as oats and lettuce, which have a rough husk-like 
covering that retains air when the seeds are immersed. 
The method does not give so striking results with seeds not 
having a rigid seed-coat but having relatively large cotyledons, 
as peas, or having a large quantity of endosperm, as maize, as it 
does with seeds having a rigid seed-coat, such as grape seed, 
pepper, egg-plant, etc. In the hands of the writer the method 
has given no positive results at all with corn or with beans. 
Correlations between specific gravity of seed and vigor of the 
resulting seedling are less close than correlations between the 
specific gravity of the seed and its germination; nevertheless such 
correlations do exist, it appears, in sufficient degree to make them 
of value in practice. 
» 
BIBLIOGRAPHY. 
In this bibliography are comprised such references to the sub- 
ject of specific gravity of seeds as have come to the writer’s atten- 
tion in the course of a rather limited survey of the literature. 
They are taken in larger part from the Samenkunde of Nobbe and 
the Saat und Pflege der landwirtschaftlichen Kulturpflanzen of 
Wollny. The subject of specific gravity of seed has been worked 
up in various monographs, especially in those of Marek and 
Schertler, as also in the Samenkunde of Harz; but to these works 
the writer has not had access. 
Since the manuscript of this bulletin was prepared for the 
printer the writer has learned that Dr. T. L. Lyon of the Nebraska 
Experiment Station is about to publish from the Plant Breeding 
Laboratory of the U. S. Department of Agriculture, a report of 
extended investigations on the relations between specific gravity 
and other properties, such as composition and size of grain in 
wheat kernels. The writer regrets that Dr. Lyon’s work has not 
already appeared so that a review of it might be included in this 
report. 
References in the following bibliography, such as “ Cited by 
Wollny ” or “ Cited by Nobbe,” refer to the two works mentioned 
above. 
