50 
~ N . C. Experiment Station 
water lost by the air dry seeds during the period of preliminary drying, 
the water remaining in the seeds at the end of the period of preliminary 
drying was calculated and is given in the table as percentage of the oven 
dry weight of the seeds. In Experiment 4 the preliminary drying was done 
at 60° C. for periods of 12, 18, and 24 hours, and in experiment 5 at 50° C. for 
24 and 36 hours. In experiment 6 the different lots were dried at 40, 45, 50. 
55, and 60° C. for a uniform period of 24 hours. In all three experiments 
the final treatment was done at 95° C. for 12 hours. After the heat treat¬ 
ments the seeds were germinated between blotters and the percentage of 
seeds which sprouted was recorded at intervals in order to get some idea 
of the rate of germination. Also the average length of the radicles of the 
seedlings which were not attacked by bacteria or fungi was determined 
at the end of the 5-day period in the germinator. 
All the seeds dried at 40° C. and all except 5 dried at 45° C. were killed 
by the subsequent treatment at 95°. During the preliminary period of 
drying these seeds lost water equivalent to 3.5 per cent or less of their air 
dry weight and retained an amount of water equal to 5.54 per cent or more 
of their oven dry weight. The two lots which were desiccated at 50° for 
24 hours and the two lots dried at 60° for 12 hours were retarded in rate 
and greatly reduced in amount of germination. These seeds lost more water 
during the period of preliminary drying than those which were dried at 
40 and 45°, but the amount retained was still too great to enable the seeds 
to withstand well the treatment at 95°. The seeds which were dried at 60° 
for 18 and 24 hours suffered no ill effects from the treatment at 95°, but on 
the contrary germination was as complete and somewhat more prompt than 
in untreated check seeds. During the desiccation at 60° these seeds lost 
water equal to 5.24 per cent or more of their air dry weight and retained 
an amount equivalent to 3.36 per cent or less of their oven dry weight. 
In no test in which the final treatment of the seeds was at 95° for 12 hours 
and in which the seeds lost as much as 5.24 per cent of their weight during 
the period of preliminary drying did the treatment at 95° cause pronounced 
loss of viability. The lot which was dried at 55° and which lost 5.51 per 
cent of its weight appears to have suffered slight reduction in amount of 
germination. Aside from this one lot, the seeds which lost as much as 5.24 
per cent of their weight germinated more promptly and as completely as 
untreated seed. As a result of the study made in experiments 4, 5, and 6, 
a statement expressing the relation between water loss and resistance to 
high temperature may be formulated to the effect that cotton seeds may be 
conditioned to withstand a temperature of 95° C. for 12 hours by desiccating 
them at low temperatures until they have lost not less than 5.24 per cent 
of their dry weight. Obviously, this statement can apply only to seeds 
whose water content is not much greater than 8.33 per cent or 8.57 per 
cent of their air dry weight; for with seeds containing more than this 
amount of water, the removal of 5.24 per cent of their weight would still 
leave the living protoplasm too strongly hydrated to long withstand a tem¬ 
perature of 95°, while, on the other hand, seeds containing less than 8.33 
per cent of water can obviously be conditioned to withstand 95° for 12 
hours by removal of water equivalent to less than 5.24 per cent of their dry 
weight. A much more broadly applicable criterion of the ability of seeds 
