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THE POPULAR SCIENCE MONTHLY 



ture was attained, so that there was only a momentary exposure to 

 the temperatures about to be cited. Of those which had been exposed 

 to 190° Fahr., many did not germinate ; still fewer of the seeds that 

 had been exposed to 201° produced young plants, while, of those 

 heated to 212°, not one germinated. After the young plants (devel- 

 oped from seeds heated to lower temperatures) had grown for thir- 

 teen days, their capability of resisting heat was tested in the manner 

 described, and with this result. Those whose roots had been momen- 

 tarily exposed to 156° continued to live after they had been replanted, 

 while those whose roots had been exposed to 167° and upward speedily 

 dried up and perished, although, like the others, they had been re- 

 planted in carefully-watered earth. 



These were the only complete experiments made by Spallanzani 

 with plants and their seeds ; but many other kinds of seeds only, in- 

 cluding those of the broad-bean, barley, kidney-bean, maize, vetch, 

 spinach, beet-root, turnip, and mallow, were also exposed to the influ- 

 ence of heat while packed in dry sand. Although this method is less 

 exact and trustworthy, and is one with which we are not now con- 

 cerned, still it may be stated that only four of the numerous seeds with 

 which experiment was made after this fashion survived their brief ex- 

 posure in the dry state to the temperature of 212° ; all the others failed 

 to germinate. 



The abbe's researches, therefore, taught him three things : 1. That 

 eggs can endure a decidedly higher degree of heat than that proving 

 fatal to animals of the kind from which they have been derived ; 2. 

 That an analogous difference exists between seeds and plants in respect 

 to their capacity of withstanding the action of heat ; and, 3. That seeds 

 and plants can resist higher grades of heat than eggs and animals re. 

 spectively. 



After calling attention to these conclusions, Spallanzani said (p. 

 64) : " Of course I am far from pretending to explain these results ; I 

 know the difficulty of the undertaking, and wdll only venture a few 

 conjectures, at most, letting them go for what they are worth, and 

 leaving every one free to think as he pleases." As his conjectures, 

 however, cannot be much improved upon at the present day, 1 may 

 as well call the reader's attention to them by briefly pointing out their 

 nature. 



At the first glance, the abbe says, the superior power of resisting 

 heat displayed by eggs and seeds, as compared with animals and plants, 

 might be supposed to be due to the latter feeling the effects of heat 

 more rapidly, owing to their being free from those envelopes which 

 inclose the ^^2, or the seed. But the weight of this supposed reason 

 soon disappears, in the case of eggs at all events. Looking to the 

 thinness of their investing membrane, this supposition, as Spallanzani 

 says, " seems very improbable indeed, when we consider how easily 

 and how rapidly fire penetrates so thin a layer of matter." He 



