TEE CHEMISTRY OF THE FARM. 



acid. We have familiar examples of such plants in the 

 broomrape and dodder of our clover fields, and in the 

 common fungi. The broomrape and dodder are fed by 

 the juices of the plants on which they live as parasites. 

 The fungi derive their carbon from the decayed vegetable 

 matter in the soil. 



2. Formation of Organic Matter. The oxygen gas 

 given off by a green plant exposed to light is so nearly 

 equal in volume to the carbonic acid decomposed, that 

 apparently the whole of the oxygen contained in the 

 carbonic acid is returned to the atmosphere; the reac- 

 tion is, however, really more complicated, as water is 

 probably decomposed at the same time as the carbonic 

 acid. 



The exact nature of the reaction which takes place 

 when carbonic acid is decomposed in the chlorophyll cells 

 is still unknown. It is probable that formaldehyde is first 

 produced, according to the following equation : 

 C0 2 +H 2 0=CH 2 + 2 . 



From formaldehyde glucose is possibly derived by a 

 process of condensation : 



The formation of carbo-hydrates in the plant is plainly 

 dependent on the presence of nitrogenous matter, phos- 

 phates, potash, and the other essential ingredients of 

 plant-food ; a plant poorly provided with these substances 

 produces only a small quantity of carbo-hydrates, how- 

 ever much it be exposed to light. Ti:e formation of glucose 

 and starch is therefore regarded by some as due to a 

 splitting up of the nitrogenous protoplasm, the nitro- 

 genous residue left combining with formaldehyde, and 

 thus reconstituting the original nitrogenous matter. 



