THE VIABILITY OF RADISH SEEDS 305 
indicated in the tables are based upon the treatment of approximately 
sixty thousand radish seeds. The resistance of the three varieties 
proved to be so similar that a separate discussion of each is unnecessary. 
An examination of these tables shows that there is a definite 
relation between the initial water content of seeds heated at high 
temperatures and their viability. Seeds of an initial water content 
of 71 percent, 50 percent and 45 percent are killed at 60° C. As the 
water content decreases in the successive series we find the percent of 
germination to increase and the death point of the sample to be 
markedly raised. For example as the water content is decreased from 
45 percent to 30 percent the lethal temperature shifts from 60° C. to 
65° C. Air-dry seeds of approximately 4 percent water content 
give a normal germination after treating at 75° C. and are killed 
between 95° C. and 100° C. On the other hand, samples carefully 
dried until only .4 percent of water is present at the time of treatment, 
give a normal germination at 100° C. and are killed between 123° C. 
and 125° C. We find then as the water content increases from .4 
percent to 45 percent that the maximum temperature at which a 
normal percent of germination takes place drops from 100° C. to 
below 50° C. and that the lethal temperature drops from between 
I23°-I25° C. to 55°-6o° C. The resistance of radish seeds exposed 
to high temperatures decreases as their initial water content increases. 
Furthermore at temperatures high enough to be injurious, the viability 
of radish seeds of a definite initial water content decreases as the tem- 
perature to which they are exposed is raised. 
In recording the percent of daily germination not included in 
the above tables, a greater or less degree of retardation in the germina- 
tion of seeds, treated at temperatures a few degrees below their 
maximum, occurred so constantly that it was thought advisable to 
make a definite quantitative study of the same. In Table IV are 
recorded the results of a series of experiments on the rate of germina- 
tion as affected by initial water content and high temperatures. 
Samples of five hundred radish seeds containing 4 percent, 9 per- 
cent, 14 percent, and 18 percent of water, respectively, were heated 
for thirty minutes in 100 c.c. flasks submerged in a bath held at 80° C. 
and subsequently allowed to germinate on plaster of Paris blocks. 
The data (Table I) show that at this temperature seeds containing 
the above water contents suffer in direct proportion to the quantity 
of water present. The observations were carried on over a period of 
