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H. D. WAGGONER 
according to the amount of water present in the seeds when heated. 
(3) The seeds were heated in ovens. In this case it is evident that 
the air in the ovens was of low relative humidity and consequently 
the seeds lost moisture during the heating. Seed treated in this 
manner endure exceedingly high temperatures without apparent injury. 
It seemed desirable to make a detailed study of the resistance of 
seeds of different water contents to high temperatures under carefully 
controlled conditions. Accordingly, experiments were carried on in 
the laboratories of plant physiology under the direction of Professor 
Chas. F. Hottes, to whom the writer is greatly indebted for searching 
criticism and helpful suggestion. 
In taking up this subject anew two closely related lines of experi- 
mentation were outlined. The one was concerned with the effect of 
high temperature upon series of samples of seeds of increasing water 
content. The other was to determine the cause for the wide difference 
in the resistance of seeds treated by the three methods indicated 
above. A survey of the more pertinent literature will serve to bring 
these two points definitely before us. 
As early as 1859, Heiden reported that grains of barley, when 
exposed for one hour to dry air at 90° C. germinated, while similar 
grains heated in water at 60° C. for the same period of time were killed. 
In 1865, Fiedler (Sachs), working with seeds of pea, rye, flax, barley 
and corn, showed that swollen seeds were killed at from 50° C. to 
60° C, while those containing less moisture withstood 70° C. or more. 
The seeds were treated in closed test tubes immersed in water main- 
tained at the desired temperature. Von Hohnel (1877) improved the 
method as used by Fiedler in that he covered the seeds in the test 
tubes with fine metal filings to facilitate the transfer of heat. He 
worked with seeds of a number of different species and reported that 
most of them when sufficiently dried were able to endure an exposure 
at 110° C. for sixty minutes. Some, heated at 125° C. for fifteen 
minutes were found viable. Just (1875, 1877) reports that clover 
seeds heated in a saturated atmosphere at 50° C. for forty-eight hours, 
or at 75° C. for one hour, lost their viability. However, if the seeds 
were well dried they could endure a temperature of 120° C. Other 
kinds of seeds gave similar results. Detmer (1880) records that the 
viability of seeds is not lost in boiling water, provided they are not in 
a swollen state. He further states that the less moisture seeds contain 
at the time of treatment the greater is their resistance to high tempera- 
