"Thus, as a general average, the amount of carbon removed from the atmosphere by growing plants is no greater than the amount returned to the air by these various forms of combustion or decay. In like manner the supply of combined oxygen is maintained, both carbon and oxygen being furnished to the plant m the carbon dioxid. "As a matter of fact, the air consists very largely of oxygen and nitrogen, both in the free state, but in this form these elements cannot be utilized in the growth of agricultural plants. The only apparent exception to this is in case of legume crops, such as clover, alfalfa, peas, beans, and vetch, which have power to utilize the free nitrogen by means of their symbiotic relationship with certain nitrogen-fixing bacteria which live, or may live, in tubercles on their roots. "Carbon and oxygen constitute about ninety per cent. of the dry matter of ordinary farm crops, and with the addition of hydrogen very important plant constituents are produced; such as starch, sugar, fiber, or cellulose, which constitute the carbohydrate group. As the name indicates, this group contains carbon, hydrogen, and oxygen, the last two being present in the same proportion as in water. "Water is composed of the two elements, hydrogen and oxygen, both of which are gases in the free state. Water is taken into the plant through the roots and decomposed in the leaves in contact with the carbon dioxid under the influence of sunlight and the life principle. The oxygen from the water and part of that from the carbon dioxid is given off into the air through the breathing pores, while the carbon, hydrogen, and part of the oxygen, unite to form the carbohydrates. These three elements constitute about ninety-five per cent. of our farm crops, and yet every one of the other seven plant food elements is just as essential to the growth and full development of the plant as are these three." "Then so long as we have air above and moisture below, our crops will not lack for carbon, oxygen, and hydrogen. Is that the summing up of the matter?" "Yes, Sir," Percy replied. "And those three elements make up ninety-five per cent. of our farm crops. Is that correct?" "Yes, Sir, as an average." "Well, now it seems to me, if nature thus provides ninety-five per cent. of all we need, we ought to find some way of furnishing the other five per cent. It makes me think of the young wife who told her husband she could live on bread and water, with his love, and he told her that if she would furnish the bread he'd skirmish around and get the water. But, say, did that South Carolina man use any fertilizer for that immense crop of corn?"