138 EXPERIMENTAL EVOLUTION LECT. 



water ; in the second, it was 90 Cent., and the time 

 for heating was ten minutes ; in the third, the seeds 

 remained two minutes only in the water at 90 Cent. 

 The final result was that in the first series only one 

 sort of seed was able to withstand the effects of the 

 heat : two out of ten seeds germinated. In the 

 second series one seed only germinated (Lepidium 

 sativum}, and in the third series two species ger- 

 minated (cress and radish). 



The same result was obtained when I planted seeds of 

 different sorts whichhad been subjected to the influence 

 of a solution of sulphate of copper in water, during a 

 period varying from one to sixteen days. Some species 

 were very sensitive, and did not germinate at all. Such 

 was the case with radish and mustard seed. Others 

 were less sensitive, and Lepidium sativum germinated 

 even after ten days' immersion, but then only some of 

 the seeds were able to germinate, and the proportion of 

 those that were killed increased when the duration of 

 the submersion was greater. Lastly, flax seed withstood 

 sixteen days' contact with the copper solution, but the 

 number of germinations was larger among the seeds 

 which had been immersed four or eight days only, than 

 among those which had remained the whole period. 

 More recent experiments of the same sort with 

 copper and strychnine have yielded the same results, 

 and show that : istly, great differences occur in the 



