CHAPTER II. 



VKGETAL NUTRITION. 



In the composition of every plant we find mineral substances, 

 ternary substances non-azotised and proteic substances. Now 

 plants not eating each other direct, like animals, it is needful for 

 the vegetal organic substances to be habitually created by the 

 plant itself, at the expense of the mineral medium which 

 environs it. Brought back to their primary mineral elements, 

 the complex organic substances yield carbon, oxygen, hydrogen, 

 azote, and a certain quantity of sulphur and of phosphorus. If 

 we add to these elements chlore, calcium, silicium, potassium, 

 sodium, magnesium, lithium, iron, often manganese, and in the 

 marine plants, iodine and brome, we have neai-ly the whole 

 elementary soiu-ces of alimentation in the vegetal kingdom. 

 Naturally the metals which we have just enumerated form bases 

 which combine with the acids which they encounter, to consti- 

 tute sulphates, silicates, chlorures, often organic salts, for 

 instance, oxalates, and so on. 



To foi-m a sufficient idea of vegetal nutrition, we must follow 

 these mineral elements, note how they enter into the plant, 

 indicate the combinations which they form there, finally, leave 

 them only when, having played out their part in the vegetal 

 organism, they are finally expulsed from it. 



Of these chemical elements, some, for example, are derived 

 from the air, others from the soil. The mineral elements taken 

 direct from the ambient air by the plant are hydrogen, oxygen, 

 carbon. Hydrogen and oxygen are absorbed and fixed by the 



