CHEMICAL MANURES. 11 



can watch their growth from day to day, which we will soon find is 

 governed by a geometrical regularity not to be thrown off. 



Here the growth is -made by successive and continued deposits of 

 salt, the first crystals being centres of attraction for the molecules of 

 sugar and salt diffused through the liquid. 



The work of vegetable growth is not so simple, though the phases 

 through which a vegetable passes before its full development have a 

 character of fixedness and persistency which excludes all idea of 

 chance and whim. The laws governing it are not less inflexible than 

 those governing minerals, and their principles and details are equally 

 well known. 



I have told you that plants owe their formation to fourteen different 

 elements. I now add that some of these elements are in the form of 

 aerial gases, while others, liquid or solid, issue from the soil. The 

 first are absorbed by the leaves, the second by the roots. Thus, 

 plants are formed from many and very different principles, drawn 

 from varied sources. But these principles do not at once build up 

 tissues and organs ; they first pass through a stage belonging rather 

 to inorganic than to organic nature. 



The formation of a plant is, then, in reality an operation of two 

 degrees. 



These compounds of uncertain form are divided into two groups, 

 the one comprehending those compounds into which only carbon, 

 hydrogen and oxygen enter ; the other, those in which most azote, 

 sulphur and phosphorus are found. 



Here is a list of these products, which I will call transitory 

 products of active vegetation, to recall at once their origin, principal 

 character and true distinction. 



Transitory Products. 



Hydrocarbonates. Azotes. 



Insoluble in water, { Cellulose, . 



' ( Amidon (starch). Fibrin. 



C Gum-dragon, 

 Semi-solubles, < Pectin, 



(^ Inulin. Casein. 



I Gum-arabic, 

 Mucilage, 

 Grape sugar, 

 Cane sugar. Albumen. 



We will take first the products of the first group. All these pro- 

 ducts, to which w r e will give the name hydrates of carbon, have a 

 common character ; their composition is the same. For greater dis- 

 tinctness, we w r ill express them by the common formula, C 12 (HO) n . 



In all there are twelve equivalents of carbon, always in combina- 

 tion with hydrogen and oxygen in proportions to form water. 



Although unlike in appearance, all these bodies are, in reality, but 

 reproductions of the same type. The proof of this is the impossi- 

 bility to draw a line of demarkation between them; so, instead of 

 taking them separately in a single plant, we will notice the variations 



