34 NOURISHMENT OF PLANTS. 



been obtained by modern investigation into all the 

 sources connected with the supply of these nutrients, 

 the following answer must be given to the above 

 inquiry. 



1. Plants receive their oxygen and hydrogen from 

 ivatefj without which, indeed, it is, generally speak- 

 ing, wholly impossible that they can live and thrive. 

 In addition to this fact, water is indispensable to 

 vegetation, because it supplies a medium for dis- 

 solving all those nutritive ingredients which cannot 

 of themselves become fluid or aeriform, and because, 

 moreover, it occasions by its fluid constitution the 

 formation of the solid vegetable parts ; for it is 

 from the juice made liquid by the water, that all the 

 solid constituents of plants are produced or elab- 

 orated. 



2. Plants absorb carbon in the form of carbonic 

 acid, which enters as an unfailing constituent into 

 our atmospheric air and spring-water, and is formed 

 in every soil that contains humus. Carbonic acid is 

 a kind of air which is unceasingly generated in ex- 

 traordinary quantities by the three chemical pro- 

 cesses most universally diff*used in nature ; we 

 mean, the respiration of men and animals, the com- 

 bustion of wood, coal, etc., and the putrefaction or 

 decay of animal and vegetable matter. It is, more- 

 over, evolved in fermentation, and causes the effer- 

 vescence and foaming of the fermenting mass, as 

 likewise the sparkle of beverages not thoroughly and 

 completely fermented ; viz. bottled ale. Champagne, 



