FUNCTION.] SEEDS CAN BEAR A HIGH TEMPERATURE. 263 



apparently suffer, by being exposed for a quarter of an hour 

 to a temperature equal to freezing mercury : such grains 

 were afterwards placed in a proper situation, and germina- 

 tion took place as usual. Considering that the particles of 

 fsecula of which seeds consist are not liable to bursting below 

 a temperature of 75 centig. (167 Fahr.), these observers 

 were led to ascertain how near an approach to this extreme 

 temperature might be made, without destroying vegetable 

 life. Seeds of various cereal and leguminous plants were 

 placed for a quarte r of an hour in water of this temperature, 

 and they were all killed ; five minutes were afterwards ascer- 

 tained to suffice for the destruction of three in five. Less 

 elevated temperatures were next experimented on. Wheat, 

 Barley, Kidneybeans, and Flax were killed in 274- minutes, 

 by water at 62 centig. (143- 6 Fahr.) ; a few grains of Rye 

 and some Beans required a longer exposure to be destroyed. 

 When the temperature was lowered to 52 centig. (125 '6 

 Fahr.), most of the seeds in experiment retained their 

 vitality; but even this was fatal to Barley, Kidneybeans, 

 and Flax. 



Fluid water has conducting powers very different from 

 those of vapour or of dry air ; it was thereupon important, to 

 determine whether the temperature that seeds can bear is 

 regulated by the nature of the medium in which they are 

 exposed to it. In vapour, 75 centig. (167 Fahr.) was suffi- 

 cient to destroy such seeds as were exposed; but, at 62 

 centig. (143' 6 Fahr.), they retained their vitality, after 

 having been under experiment for a quarter of an hour. 

 But, in dry air, many seeds bore the temperature of 75 

 centig. (167 Fahr.), for a quarter of an hour, without incon- 

 venience. Hence it appears that seeds in steam can bear 12 

 centig. more than in water, and in dry air 13 centig. more 

 than in steam. 



In these experiments, the action of temperature was ex- 

 tremely rapid. In lowering the temperature and prolonging 

 its action, it was found that, when Wheat, Rye, and Barley 

 were exposed for three days, in water, to a temperature of 

 35 centig. (95 Fahr.), four-fifths of the Wheat and Rye, 

 and all the Barley, were killed. Hence it would appear, 



