The farmer, then, in his work on the farm deals with certain agents, chief among which are Soils, Plants, Animals, Tools and Buildings. Other agents which assist or retard his work according to circumstances are the air, sunlight, heat, moisture, plant food, microscopic organisms called bacteria, etc. These agents are controlled in their relations to one another by certain forces which work according to certain laws and principles of nature. To work intelligently and to obtain the best results the farmer must become familiar with these agents and must work in harmony with the laws and principles which control them. Let us take up the study of some of these groups of agents, beginning with the most important or central one on the farm. Which do you think is the most important group? Some will say "tools." The majority will probably say, study the soil first, "because we must work the soil before we can grow good crops." Some few will mention "plants." This last is right. The farm animals are dependent on plants for food. We till or work the soil to produce plants. Plants are living, growing things, and certain requirements or conditions are necessary for their growth and development; we cannot intelligently prepare the soil for plant growth until we know something about the work of plants and the conditions they need to do their work well. For our first study of plants let us get together a number of farm and garden plants. Say, we have a corn plant, cotton, beet, turnip, carrot, onion, potato, grass, geranium, marigold, pigweed, thistle, or other farm or garden plants. In each case get the entire plant, with as much root as possible. Do these plants in any way resemble one another? All are green, all have roots, all have stems and leaves, some of them have flowers, fruit, and seeds, and the others in time will produce them. Why does the farmer raise these plants? For food for man and animals; for clothing; for ornamental purposes; for pleasure, etc. [Illustration: FIG. 1.--SPECIMEN PLANTS FOR STUDY.] [Illustration: FIG. 2. The first effort of a sprouting seed is to send a root down into the soil.] [Illustration: FIG. 3. Germinating seeds produce roots before they send a shoot up into the air.] Which part of any or all of these farm plants is of greatest importance to the plant itself? I am sure that you will agree that the root is the part most important to the plant itself, for if any part of a plant be separated from the root, that part ceases growth and will soon die, unless it is able to put out new roots. But the root from which the plant was cut will generally send up new shoots, unless it has nearly completed its life work. When a slip or cutting is placed in water or in moist sand it makes a root before it continues much in growth. When a seed is planted its first effort is to send a rootlet down into the soil.