242 HOW CROPS GROW. 



The roots of a plant make their first issue independently 

 of the nutritive matters that may exist in their neighbor- 

 hood. They are organized and put forth from the plant 

 itself, no matter how fertile or sterile the medium that 

 surrounds them. When they attain a certain develop- 

 ment, they are ready to exercise their office of collecting 

 food. If food be at hand, they absorb it, and, together 

 with the entire plant, are nourished by it they grow in 

 consequence. The more abundant the food, the better they 

 are nourished, and the more they multiply. The plant 

 sends out rootlets in all directions ; those which come in 

 contact with food, live, enlarge, and ramify ; those which 

 find no nourishment, remain undeveloped' or perish. 



The Quantity of Roots actually attached to any plant 

 is usually far greater than can be estimated by roughly 

 lifting them from the soil. To extricate the roots of 

 wheat or clover, for example, from the earth, completely, 

 is a matter of no little difficulty. Schubart has made the 

 most satisfactory observations we possess on the roots of 

 several important crops, growing in the field. He sepa- 

 rated them from the soil by the following expedient : An 

 excavation was made in the field to the depth of 6 feet, and 

 a stream of water was directed against the vertical wall 

 of soil until it was washed away, so that the roots of the 

 plants growing in it were laid bare. The roots thus ex- 

 posed in a field of rye, in one of beans, and in a bed of gar- 

 den peas, presented the appearance of a mat or felt of white 

 fibers, to a depth of about 4 feet from the surface of the 

 ground. The roots of winter wheat he observed as deep 

 as 7 feet, in a light subsoil, forty-seven days after sowing. 

 The depth of the roots of winter wheat, winter rye, and 

 winter colza, as well as of clover, was 3-4 feet. The roots 

 of clover, one year old, were 3^- feet long, those of two- 

 year-old clover but 4 inches longer. The quantity of roots 

 in per cent of the entire plant in the dry state was found 

 to be as follows. ( Chem. Ackersmann, I, p. 193.) 



