CHEMICAL MANURES. 13 



materials which form the second group of transitory products of 

 vegetable activity are three in number ; they are distinguished from 

 the hydrates of carbon by the azote, sulphur and phosphorus they 

 contain, which are wanting in the first. 



Their composition is then one more degree complicated. We will 

 observe the same of them as has already been said of the hydrates of 

 carbon : in spite of their dissimilarity, they are in reality the same 

 body under three different conditions. Their composition is the same 

 and is expressed by the same formula, C I44 , H 112 , Az 18 , S 2 , O 44 . 



Is it objected that fibrin is insoluble in water while casein and 

 albumen are soluble ? But I say, Bring water to the boiling point 

 and these two bodies will be equally insoluble. 



But you will say, Heat does not dissolve albumen as it does casein 

 that albumen coagulates in masses, while casein coagulates but in 

 part, in the form of a skin on the surface of the liquid. To refute 

 this objection, we need only communicate the properties of whichever 

 one of these materials we please to the other two. 



Fibrin is insoluble. To make it soluble we have only to pound it 

 in a marble mortar and add a fiftieth part of its weight in caustic 

 soda. The dissolution thus produced possesses all the properties of 

 albumen, and its most characteristic one, that of coagulating in a 

 mass under the action of heat. 



If you pour a few drops of caustic soda into a solution of albumen, 

 it will acquire the property of 'coagulating in parts and forming a 

 skin like casein. 



If I add finally, that these bodies, like the hydrates of carbon, are 

 continually changing into each other during the periods of vegetable 

 life, you will agree with what I have already said, that they are varied 

 forms of the same type. 



Let us pause a minute at these transformations, which make the 

 very essence of vegetable life. 



Wheat, before germinating, contains from ten to fifteen per cent, 

 of fibrin and one or two per cent, of albumen, more or less. As soon 

 as germination begins, the proportion of fibrin diminishes and that 

 of albumen increases. Beans and lentils contain no fibrin, but casein 

 has, like cheese, a very little albumen ; now during germination the 

 casein disappears and the albumen takes its place. It is the same 

 with amidon, contained in abundance in seeds : it is changed into 

 gum and sugar, and they in their turn become cellulose in the leaves, 

 branches and roots. 



The plant in its first period is but the seed transformed. After 

 germination, when vegetation may properly be said to commence, it 

 receives more and more albumen until the time of flowering, when in 

 wheat the albumen becomes fibrin, and casein in beans and lentils. 



Let us return to the hydrates of carbon, taking the beet for ex- 

 ample. Before flowering it contains eight or ten per cent, of sugar ; 

 after the seed is formed the sugar disappears, amidon having taken 

 its place. 



I therefore repeat, vegetable nutrition is a phenomenon of two 

 stages, the first corresponding to tho formation of transitory 



