302 
H. D. WAGGONER 
The problems before us then are: (i) to determine the definite relation 
between the water content of seeds exposed to high temperatures 
and their viability ; and (2) to explain the different degrees of resistance 
of seeds exposed to high temperatures when treated by different 
methods. 
Materials and Methods 
The seeds used in these experiments were Icicle, Black Spanish 
Winter and Crystal Forcing radish obtained from Henry A. Dreer, 
Philadelphia. These were selected with the view of comparing the 
relative resistance of varieties adapted to widely different cultural 
conditions. The seeds were of good quality and throughout the 
experiments tested at approximately 90 percent. They were stored 
in glass-stoppered bottles and kept in a room where the humidity of 
the air varied but little ; the moisture (4 percent) in the seeds remained 
practically constant throughout the experiments. A tin measure was 
used to obtain random samples from the bottles and no selection was 
made other than that the seeds with ruptured coats were discarded. 
Three methods were used in heating the seeds. (i) The samples 
were placed in Florence flasks of 100 c.c. capacity, the bottoms of which 
were sufficiently large to allow each seed to come in direct contact with 
the glass. The flasks were placed in a wire cage and entirely sub- 
merged in a bath containing about thirty-five liters of water previously 
heated to the desired temperature. This large quantity of water, 
kept in circulation by a Kohler stirrer, rendered it possible to maintain 
a temperature constant to within one half of a degree Centigrade. 
Increase in pressure during the heating was guarded against by pro- 
viding the containers with corks through which capillary tubes thirty 
centimeters long were passed. Temperatures above the boiling point 
of water were obtained by adding the requisite amount of calcium 
chloride to the water of the bath. In these latter experiments pro- 
vision was made for replacing the water evaporated from the bath 
while the experiments were in progress. (2) The samples in shallow 
open pans were placed in a double-walled copper oven filled with 
glycerine. The temperature was controlled to within one half of one 
degree Centigrade. (3) The samples were enclosed in muslin bags 
and immersed directly in the water of a bath previously heated to 
the desired temperature. 
The water content of the stored seeds was determined by finding 
the loss in weight of a random sample brought to constant weight in 
