SEC?. II. GASES. 



SUBSECTION II. 



Oxygene. As oxygene is essential to the com- 

 mencement and progress of germination ; so also 

 it is essential to the progress of vegetation. This 

 is clearly proved by the following experiments of 

 Saussure : Having pulled up some young plants of 

 the Horse-chesnut, furnished with their leaves and 

 weighing about 4 60 grains, he introduced their roots, 

 which were nearly a foot in length, into receivers 

 of about sixty cubic inches in capacity, and luted 

 the base of the stem to the neck of the receiver. 

 Into one of the receivers, each of which contained 

 a quantity of distilled water, he introduced twenty- 

 eight cubic inches of nitrogene which was in con- 

 tact with the upper part of the root, while the 

 under part was immersed in the water. Into 

 another he introduced an equal quantity of hy- 

 drogene ; and into a third an equal quantity of 

 carbonic acid. The plant whose root was in con-itsbene- 

 tact with the carbonic acid died in the course of flu^'at 

 eight days : the others lived a fortnight, but had * plied to 

 not diminished the volume of their atmosphere. 

 But plants which were placed at the same time in 

 a similar apparatus, furnished with atmospheric air, 

 gave a very different result ; for at the end of three 

 weeks when the experiment was stopped, they were 

 still fresh and vigorous^ and the volume of their at- 



