484 THE UNIVERSE. 



ing to Saussure and Woodhouse, as much as a hundredth 

 part. 



At the time when seeds germinate they exhale carbonic 

 acid and water, and set free a noticeable amount of heat. 



Divers causes accessorily hasten the evolution of the 

 plant. 



Electricity is one of these. It was the Abbe Nollet who 

 discovered its action. More recently Sir Humphry Davy 

 and A. Becquerel observed that it is only negative elec- 

 tricity that gives energy to this phenomenon ; whilst posi- 

 tive electricity, on the contrary, retards it. 



Indeed, if we pass an electric current beneath a sown 

 surface, the seeds develop much more quickly than in a part 

 which has not been submitted to electricity. 



The difference is well marked when we experiment with 

 seeds which germinate very quickly. One patch will be 

 covered with close green vegetation, while on the other not 

 a single plant has yet issued from the ground. 



Following Ingenhouz and Sennebier, men have long 

 taught that light was opposed to germination. This is an 

 error, as Saussure noticed. Nevertheless, all the colored 

 rays of light are not favorable to it ; the chemical and the 

 calorific rays have each an opposite action upon this phe- 

 nomenon. The former, which are the blue and the violet 

 rays, clearly increase its activity ; the latter, the red and 

 yellow rays, are hurtful to it. 1 



1 With regard to the action of light, the balance of evidence seems to be in 

 favor of the opinion expressed by Mr. Hunt, which is very much to the same ef- 

 fect, namely, that the blue rays promote germination, while the yellow light-giv- 

 ing rays impede it. Popular Science Review. Tr. 



