M. Dumas on the Chemical Statics of Organized Beings. 459 



when they are taken into consideration) it is no longer diffi- 

 cult to understand the important part that the decomposition 

 of carbonic acid performs in plants. 



Hydrogen. — In the same manner that plants decompose car- 

 bonic acid for the appropriation of its carbon, and in order 

 to form together with it all the neutral bodies which compose 

 nearly their entire mass, in the same way, and for certain 

 products which they form in less abundance, plants decom- 

 pose water and fix its hydrogen. This appears clearly from 

 M. Boussingault's experiments on the vegetation of peas in 

 closed vessels. It is still more evident from the production 

 of fat or volatile oils so frequent in certain parts of plants, and 

 always so rich in hydrogen. This can only come from water, 

 for the plant receives no other hydrogenated product than the 

 water itself. 



These hydrogenated bodies, to which the fixation of the 

 hydrogen borrowed from the water gives birth, are employed 

 by plants for accessory uses. They form indeed the volatile 

 oils which serve for defence against the ravages of insects ; 

 fat oils or fats, which surround the seed, and which serve to 

 develop heat by oxidation {en se brillent) at the moment of 

 germination ; waxes with which leaves and fruits are covered 

 so as to become impermeable to water. 



But all these uses constitute some accidents only in the life 

 of plants ; thus the hydrogenated products are much less ne- 

 cessary, much less common in the vegetable kingdom than 

 the neutral products formed of carbon and water. 



Azote. — During its life, every plant fixes azote, whether it 

 borrows the azote from the atmosphere, or takes it from the 

 manure. In either case it is probable that the azote enters 

 the plant and acts its part there only under the form of am- 

 monia or of nitric acid. 



M. Boussingault's experiments have proved that certain 

 plants, such as Jerusalem artichokes, borrow a great quantity 

 of azote from the air ; that others, such as wheat, are on the 

 contrary obliged to derive all theirs from manure ; a valuable 

 distinction for agriculture; for it is evident that all cultivation 

 should begin by producing vegetables which assimilate azote 

 and air, to rear by their aid the cattle which will furnish ma- 

 nure, and employ this latter for the cultivation of certain 

 plants, which can take azote from the manures only. 



One of the most interesting problems of agriculture consists 

 then in the art of procuring azote at a cheap rate. As for car- 

 bon, no trouble need be taken about it; nature has provided 

 for it ; the air and rain water suffice for it. But the azote of 

 the air, that which the water dissolves and brings with it ; the 



