44 
■N". C. Experiment Station 
vapor, all were killed at 75° C., but at 62° C. little harm was done, whereas 
when heated for 15 minutes in dry air at 75° C. many were capable of 
germination. It was thus found that the medium in which the seeds were 
heated determined the temperatures that they were able to endure without 
loss of germinative power. 
In 1879, Noble 44 heated wheat, rye, and oats seeds having a water content 
had been heated for one hour in water at 55° C. and that all were killed 
when heated at 60° C. When heated in dry air, the seeds endured tem¬ 
peratures of 65° C. for 4 hours, 85° C. for 30 minutes, and 90° C. for 15 
minutes, but all were killed in 15 minutes by a temperature of 95° C., and in 
10 minutes by a temperature of 100° C. 
In 1863, Haberlandt 29 heated 88 species of dry seeds in dry air at 100° C. 
for 48 hours. Twelve species entirely lost their power to germinate, 12 
species suffered partial killing, and 64 species gave full germination, many 
of this last group, however, showing marked retardation. When the same 
kinds of seeds were heated at 87.5° C. for 48 hours, only 2 species com¬ 
pletely lost their power to germinate, 17 species were partially killed, 34 
species showed marked retardation of germination, and 35 species manifested 
an acceleration of germination. No injury was observed to result from 
on application of a temperature of 56-57° for 48 hours. 
Haberlandt 20 also studied the effect of inbibed water on the viability of 
seeds of rye, corn, flax and peas. Air dried seed and seeds which had 
been allowed to swell in water at a temperature of 12 to 15° C. for 24 
hours were heated in water at a temperature of 30-55° C. for periods of 
5-10 hours. With every species, the soaked seeds proved the more suscepti¬ 
ble to the injurious effects of heat, as evidenced by the greater reduction 
of total percentage of germination and more pronounced retardation in 
rate of germination. 
In 1897, Noble 44 heated wheat rye, and oat seeds having a water content 
of 12 to 13 per cent at temperatures of 40 to 100° C. in dry air. Wheat 
and rye suffered no destruction of vitality when heated at 80° C. for a 
period of time sufficiently long to reduce the water content to 1 or -2 per 
cent. Heating at 90° €. for 2 days, whereby the water content was reduced 
to less than 1 per cent, first lessened the power of germination, and a 
temperature of 100° C. for 24 hours almost completely destroyed it. Oats 
was reported to be more susceptible to high temperatures than wheat or 
rye. Drying oats for 3 days at 50° and 60° strongly retarded and delayed 
germination. 
In 1899, Jodin 3S showed that the water content of seeds profoundly in¬ 
fluences the time which they can survive high temperatures. This worker 
heated wheat seed in a vacuum to a temperature of 100° C. without de¬ 
stroying its power to germinate. Pea and cress seeds were killed when 
heated at 98° C. for 6 hours, but when seed from the same lots were heated 
at 60° C. for 24 hours, then at 98° C. 30 per cent of the peas and 60 per cent 
of the cress still germinated. When seeds were heated in sealed tubes at 
40° C., they were killed in 20 days, but, when the seeds were sealed up with 
CaO, germination was not reduced by heating for 206 days at 40° C. 
Dixon ( 18 , 17 ) in 1901 and 1903 found that seeds of many species which had 
been dried over H 2 S0 4 or in an oven which was slowly raised to a tem¬ 
perature of 90° could thereafter endure, without complete loss of ability 
