56 FOOD OF THE VEGETATING PLANT. CHAP. I. 



air weighed five grains. Carbonic acid gas, there- 

 fore, as applied to the leaves and branches of plants, 

 is prejudicial to their vegetation in the shade, if 

 administered in a proportion beyond that in which 

 it exists in atmospheric air. 



Its influ- But it is also beneficial to the growth of the 

 pHedtotepl ant when applied to the root. This Saussure as- 

 certained by experiment also. Two boards pierced 

 with a number of holes were made to float in two 

 vessels filled, one with distilled water, and the 

 other with water impregnated with carbonic acid 

 gas. On each of these boards was placed a number 

 of Peas that had been lately made to germinate in 

 distilled water. Their radicles at the commence- 

 ment of the experiment were two lines and a half 

 long. At the end of ten days the roots in contact 

 with the distilled water were longer by five inches, 

 than those in contact with the acidulated water; 

 and the stalks and leaves were developed in the 

 same proportion. But at the end of a mpnth the 

 plants vegetating in the acidulated water had ac- 

 quired the same dimensions as the others, and at 

 the end of six weeks had considerably surpassed 

 them. It follows, therefore, that carbonic acid gas 

 as applied to the roots of plants is also beneficial 

 to their growth, at least in the more advanced 

 stages of vegetation. 



