346 Report or THE HortricuLTuRAL DEPARTMENT OF THE 
who simply made up a solution until one-half of the seeds had 
sunk. Many of his figures agree with the optimum as deter- 
mined by the present writer; but in some cases our results are 
widely at variance. For instance, he gives the specific gravity 
of grape seeds at 1.06, whereas as a matter of fact the optimum 
for grape seeds, including vinifera varieties, which were what 
Renz probably used in making his determinations, ranges from 
about 1.10 to 1.18 or 1.16. In many varieties, especially the 
stronger growing ones such as Concord, seeds of the specific gray- 
ity of 1.06 do not germinate. 
Nobbe refers also to determinations by v. Grevenitz and by 
Hoffman, neither of which are of value. Hianlein has also 
reported determinations of the specific gravities of thirteen kinds 
of seeds. 
RANGE AND DISTRIBUTION OF SEEDS WITH RESPECT 
TO SPECIFIC GRAVITY. 
The most casual examination of some of the tables given later 
on in this report (see for instance Tables II and VIF) reveals the 
fact that while the seeds of any kind of plant are distributed 
through a wide range of specific gravity, most of them are com- 
monly found within a relatively narrow range or within two such 
ranges. If the seeds are of good quality and high in percentage 
of germination, most of them are found near but not at the 
maximum specific gravity. Such distribution is shown in Table 
VII and Chart II. If, however, the seeds in their fresh condi- 
tion are low in percentage of germination and are of poor quality, 
many of them are found at or near the opposite extreme of the 
series of separates. This fact is brought out in Table II and 
Chart I, in which is shown the relative distribution of seeds of 
an imperfectly self-fertile variety of grape close-pollinated. 
All the common kinds of farm and garden seeds that the writer 
has examined show some floaters, that is, seeds that float on 
pure water. The range of density in different kinds of seeds is 
very unlike. Within the limits of the same species different 
varieties show different specific gravities, sometimes quite mark- 
edly so. This point is brought out in Table I, showing the dis- 
tribution of seeds of numerous varieties of grapes. 
