READING-LESSON 



CORNELL READING-COURSE ^°- ^• 



FOR FARMERS. i march, i899. 



By B M. DUGGAR. 



How the Plant Gets its Food from the Air. 



I . Charcoalis largely carbon , and carbon enters abu?idanth' into the 

 composition of all plants. — Half or more of the bulk of the tree, 

 aside from water and the elements of water, is carbon. When the 

 tree is charred (or incompletely burned), the carbon remains in 

 the form of charcoal. The ordinary cultivated plant has but two 

 sources from which to obtain food — the air and the soil. In a corn 

 plant of the roasting- ear stage, the water forms about eighty per 

 cent of the structure. There is, then, about twenty per cent of 

 dry matter remaining after the water has been driven off. In order 

 to form some idea of what portion of the plant structure comes from 

 the air, note that when such a corn plant is burned in air, the 

 amount of ash remaining is about one per cent of the total sub- 

 stance. This ash consists of practically all of the fertilizers 

 which we found in Reading-Lesson .No. 3 to come from the soil, 

 with the exception of the nitrogen. The entire nitrogenous 

 product forms about two per cent of the total green substance. 

 It was driven off by the burning. Next note what happens 

 when a plant is burned without free access of air, or smothered, 

 as in a charcoal pit. The mass of charcoal resulting is almost 

 as large as the body of the plant. Carbon is the element now 

 present which was not present in the ash. 



Charcoal is almost pure carbon, the ash present being so small 

 in proportion to the large amount of carbon that we look upon 

 the ash as an impurity. The fact is that the carbon and the 

 elements of water (hydrogen and ox3^gen) make up more than 

 ninety per cent, of the dry matter of the corn plant. 



The percentage of dry matter which comes from the soil may 



Note. — In this treatment of the relation of the plant to the air, only 

 the higher or agricultnral plants are referred to. 



